03 - testing and pregnancy web

8/8/2019 03 - Testing and Pregnancy WEB

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Testing and pregnancy


Genetics in Family Medicine:

The Australian Handbook for General Practitioners


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Genetics in Family Medicine: The Australian Handbook or General Practitioners 2007 Testing and pregnancy

GPs role 3

Counselling beore and during pregnancy 3

Collecting the amily history 4

Folic acid and pregnancy 4

Screening and diagnostic tests during pregnancy 5Assessing risk actors in pregnancy 5

Down syndrome and other chromosomal abnormalities 5

Neural tube deects 6

Genetic conditions and birth deects 6

Types o prenatal tests 6

Prenatal screening tests 10

Ultrasound scanning 11

Combined irst trimester screening 13

Second trimester maternal serum screening 14

Prenatal diagnostic tests 16

Chorionic villus sampling (CVS) 17

Amniocentesis 18

Ultrasound diagnostic testing 19

Genetic testing 19

Chromosome analysis 19Indications or FISH 19

Genetic conditions requiring DNA testing 20

Pre-implantation genetic diagnosis (PGD) 20

Frequently asked questions 24

Correcting misunderstandings 25

List o etal medicine services in public hospitals associated with the state genetics services in Australia 26

Bibliography 28

Further inormation 28

Patient and amily act sheets:

Preparing or pregnancy

Testing i you are pregnant

Genetics in Family Medicine: The Australian Handbook or General Practitioners 2007


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GPs role

Identiy opportunities or pre-pregnancy counselling. Collect relevant amily history. Assess whether inormation in the amily history places the current pregnancy at

increased risk.

Consider carrier tests or those rom specic ethnic groups. Provide inormation about screening and diagnostic tests during pregnancy. I necessary, reer on to appropriate Genetics Services and/or support groups. Discuss peri-conceptual olic acid supplementation, the implications o drug and medication

use during pregnancy, and other liestyle modications, eg smoking, drugs, alcohol.

Provide inormation about inectious diseases during pregnancy.

I possible, pre-pregnancy counselling is advised and should include: > Collection o relevant amily history (see Collecting the amily history below, and Family history).

> Recommending periconceptional olic acid supplementation (see Folic acid beore andduring pregnancy below).

> Provision o inormation about screening and diagnostic tests during pregnancy (see Types oprenatal tests below).

> Consideration o carrier tests or those rom specic ethnic groups, eg thalassaemia, sickle cellscreening and Tay-Sachs disease (see Haemoglobinopathies).

> Assessment o drug and medication use and implications or pregnancy.

> Discussion o liestyle changes, eg alcohol and smoking cessation during pregnancy and changesto diet.

> Provision o inormation about inectious diseases: Rubella vaccination status Varicella antibody status and immunization i non-immune Discussion about listeria inection and toxoplasmosis

> Provision o inormation about pre-implantation genetic diagnosis (PGD), or couples who are

known carriers o a genetic condition and/or couples undergoing IVF (see Pre-implantation geneticdiagnosis).

> Where couples are known carriers o a genetic condition, reer to Genetics Services.

Counselling before and during pregnancy



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Folic acid and pregnancy About 1 in every 500 pregnancies is aected by a neural tube deect.

Research has shown that 70% o cases o neural tube deects (spina bida, anencephaly, clet lip withor without clet palate) can be prevented by increasing the intake o olic acid prior to, and during earlypregnancy.

Folate is a B group vitamin ound in leay green vegetables, wholegrain breads, cereals and legumes.It is also available in tablet orms as olic acid.

Recommendations about olic acid in pregnancy

Women at population risk or neural tube deects

Women planning a pregnancy should take supplementary olic acid, 0.5mg [500g]olic acid tablet or multivitamin appropriate or use in pregnancy and containing at least0.4 mg [400g] o olic acid) every day or at least one month prior to possibleconception and continued or the rst three months o pregnancy.

As many pregnancies are unplanned, all women o reproductive age should considertaking supplementary olic acid or a olate-rich diet.

Folic acid tablets and multivitamins containing at least 0.4mg [400g] olic acid areavailable rom chemists, health ood stores and some supermarkets.

Women at increased risk or neural tube deects

Women are at higher risk o having a baby with a neural tube deect i: > They have had a baby with spina bida, anencephaly or other neural tube deects

> They themselves have had a neural tube deect

> They are on certain medications or epilepsy > They have a close relative who has had a neural tube deect.

These women should take supplementary olic acid every day or at least one monthprior to possible conception and continued or the rst three months o pregnancy.The dose recommended is usually 5mg [5000g].

Important points about olic acid

Women taking drugs to control epilepsy or seizures should ask their doctor whetherthey should increase the dose o olic acid to 5mg daily. However, specic evidence islimited in this area.

Women planning to take multivitamins to provide olic acid supplementation shouldcheck with their pharmacist or doctor whether the multivitamin dose they are planningto use contains amounts o all the other vitamins/minerals that are sae or pregnancy,as well as providing the right amount o olic acid.

Collecting the family history See Genetics in practiceor urther inormation. The amily history o the woman and her partner should be collected regarding: > Inherited conditions, eg cystic brosis, ragile X syndrome, Duchenne muscular dystrophy

> Down syndrome and other chromosomal abnormalities

> Birth deects, eg spina bida, clet lip/palate, cardiac deects > Intellectual disability

> Recurrent miscarriage

> Unexplained perinatal deaths

> Consanguinity (see Genetics in practice)

> Ethnic background



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Assessing risk factors in pregnancy

Down syndrome and other chromosomal abnormalities All women are at risk o having a baby with a chromosomal abnormality, the most common being

Down syndrome.

The risk o Down syndrome increases with maternal age, as illustrated in Figure 1.

Screening and diagnostic tests during pregnancy

The eect o maternal age on screening tests or Down syndrome

Screening tests give a risk gure or Down syndrome that modies the risk based on maternal age alone. The detection rate depends on the type o test. The detection rate and probability o an increased risk result increases with maternal age as the calculations

o risk usually include the womans age.

It is important that the woman/couple understands that screening tests will not identiy all pregnancies withDown syndrome and that an increased risk result will require urther clarication. The result rom a chorionicvillus sampling or amniocentesis will most likely still be normal.

Screening tests should be oered to all pregnant women.

Factors that increase the risk o having a baby with Down syndromeand other chromosome abnormalities

Maternal age. A previous pregnancy with a chromosome trisomy. An increased risk result on a screening test.

The presence o sot signs o Down syndrome or other etal anomalies during ultrasound examination. A parent carrying a chromosome rearrangement, eg a translocation involving chromosome 21 may increase

the risk or Down syndrome. See Chromosomal conditions.

Ageofmotheratdelivery

Figure 1. Maternal age and risk o liveborn baby with Down syndrome

Devised rom Table 2, Morris, JK, Mutton DE, Alberman E, 2005. Corrections to maternal age-specic livebirth prevalence o Down's syndrome, Journal o Medical Screening, 12:202.


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Neural tube deects

The risk o a baby having a neural tube deect: > Is approximately 0.2%, but is higher i there is a past or amily history o the condition

> Does not increase with maternal age

> Is increased or women taking certain anticonvulsants. Advice regarding risk is available rom druginormation services in obstetric hospitals or rom Genetics Services

Genetic conditions and birth deects

A amily history o a birth deect (eg congenital heart deect), inborn error o metabolism(eg phenylketonuria) or other inherited conditions (eg thalassaemia) may indicate an increased risko that condition.

A amily history should be collected rom the woman and her partner. I the woman is concerned or thereis a signicant history they should be reerred to Genetics Services or urther risk assessment, preerablyprior to conception.

Types of prenatal tests Screeningtests determine i the baby has an increased risk o having a particular

problem such as Down syndrome or a neural tube deect. They are not diagnostic andan increased risk result does not mean the baby will denitely be aected.

Prenatal screening tests include: > Ultrasound

> Early pregnancy (rst trimester) screening: nuchal translucency ultrasound togetherwith testing o the mothers blood

> Second trimester screening: testing the mothers blood (maternal serum screening)

Prenatal screening tests should not be considered routine, but rather oered as a choiceto women.

Diagnostictests determine i the baby has, or will develop ater birth, a geneticcondition. Sampling procedures to obtain cells or chromosome analysis or specicgenetic tests are invasive.

Prenatal diagnostic tests include: > Ultrasound

> Chorionic villus sampling (CVS)

> Amniocentesis

Prenatal diagnostic tests should not be considered routine, but rather oered as achoice to women.


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Figure 2. Prenatal screening and diagnostic tests oered

Pregnant

BIRTH

Screeningtests(oneonly)

Combined rst trimester

Second trimester

(blood: 10 - 12 wks +ultrasound: 113 - 136 wks)

(14 - 20 wks)

Diagnostictests

CVS a

Amniocentesis

(rom 11 wks)

(rom 15 wks)

Screening/Diagnostictests

Second trimester etal anomalyultrasound scan (18 - 20 wks)

~1% use no tests~35%

~2-3%~60%

~1% do not have etalanomaly scan aterprevious screening

The fow chart shows the possible pathways a woman may take with respect to prenataltesting. The numbers reer to the approximate percentages o women taking these options.Termination o pregnancy (TOP) is possible at any o these stages within the limitationsimposed by State and Territory laws.

a Note that the timing or oering a CVS in South Australia is sometimes rom 10 weeks gestation

~5% have had an increased risk

screening result and are thenoered a diagnostic test


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Table 1. Advantages and disadvantages o screening tests during pregnancy

Screeningtesta

Gestation(weeks)

%Downsyndromepregnanciesdetected

Advantages Disadvantages

Combined

rst trimesterscreening

10 - 12

(blood test)113 - 136(ultrasoundwith nuchaltranslucency)

85 - 90% Early screen and thereoreearly diagnosis

Highest detection rate No added risk o

miscarriage

Detection o some etalabnormalities

Benets relating toearly scan:

> Accurate dating> Diagnosis o multiple

pregnancy

> Diagnosis o earlypregnancy ailure(miscarriage)

Will detect some aectedpregnancies that mayspontaneously miscarry

Does not provide risk orneural tube deects butthe ultrasound may detectanencephaly

Women may not accessservices so early in thepregnancy

Ultrasound requiresaccredited operator oraccuracy b

Out-o-pocket expensesvary c

Secondtrimestermaternalserumscreening

14 - 20(15 - 17ideal)

70 - 75% d Available to womenpresenting in secondtrimester

No added risk omiscarriage

No out-o-pocketexpenses or publicpatients i arranged

through public hospital

Later screening test Inaccurate dates can

result in inaccurate risk bycalculations. A dating scanshould be considered idates are uncertain

Lower detection rate No neural tube risk can

be given i test done at14 weeks

Out-o-pocket expensesvary

a False positive rate set at 5% at these detection ratesb Nuchal translucency measurement should be perormed by a Fetal Medicine Foundation (FMF) and RANZCOG

(Royal Australian and New Zealand College o Obstetrics and Gynaecology) accredited operatorc May be limited access in some states: in Victoria, it is currently not unded or public patients; in Queensland

the blood test is not available publiclyd Assumes the use o the quadruple test (our analytes) and ultrasound dating


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Table 2. Advantages and disadvantages o diagnostic tests during pregnancy

DiagnosticTest

Gestation(weeks)

%Downsyndromepregnanciesdetected

Advantages Disadvantages

Chorionic

villus sampling(CVS) a

From 11

weeksb

> 99% Early detection

Denitive diagnosis Results potentially

available in time ortermination opregnancy (TOP) bycurette

Miscarriage risk (~ 1%above background in experthands)

Detects chromosomallyabnormal pregnancies thatmay otherwisespontaneously miscarry

1% risk o equivocal results(placental mosaicism ormaternal cell contaminationo sample)

0.1% ailure to detectchromosome abnormality

(abnormality is present inetus but not in placenta, ormaternal cell contaminationo sample)

Amniocentesis a From 15weeks c

100% Test with lowestmiscarriage rate

Denitive diagnosis

Miscarriage risk (~ 0.5%above background in experthands)

Diagnosis in secondtrimester, when pregnancyis more established

Results available too late orTOP by curette TOP mayneed to be perormed byinduction o labour orvaginal evacuation c

Secondtrimesteretal anomalyultrasoundscan*

(*also considered

a screening

test, seeDisadvantages)

18 - 20 Very low pick up rate onsot markersalone

Detects many physicaletal abnormalities,such as: neural tube,cardiac, limb,gastrointestinal, CNS

No added risk omiscarriage

Measures etal growthand locates position oplacenta

Not all physical abnormalitiescan be detected

Sot markers (risk actorsor chromosomalabnormalities not denitiveand dicult to interpret) 30% o babies with

Down syndrome will havesot markers/signs

Not recommended asprimary screening test orDown syndrome

a Out-o pocket expenses vary or CVS, amniocentesis and scans according to state. Public patients attending a tertiary public

hospital may not be charged i identied as increased riskb The timing o CVS is not uniorm throughout Australia, eg in South Australia it is sometimes oered rom 10 weeks

gestationc Procedures ater 20 weeks gestation may not provide results in timerame permitting second trimester termination o

pregnancy. Reer to your State abortion laws, and policies o local perinatal units


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Oering testing

All pregnant women or couples contemplating pregnancy should be oered inormation regardingscreening tests. Women should be inormed that they will be oered urther testing i they have anincreased risk result on a screening test.

All women at increased risk should also be oered inormation about diagnostic tests. All women/couples undertaking screening and diagnostic tests should be made aware that there could

be an unanticipated nding. For example, testing or Down syndrome may identiy a etus with Turnersyndrome.

I a woman decides to have prenatal testing, the best test will depend on the womans gestation, risk andher concerns. Access to services may also infuence the decision. The decision about which test is best isa personal one or each woman/couple.

Not all tests are available in the public sector and some tests do not have a Medicare rebate. Risk can be dicult or individuals to understand (see Ways o explaining prenatal risk fguresbelow).

Prenatal screening tests Types o prenatal screening tests include: > Ultrasound scanning

> Combined rst trimester screening

> Second trimester maternal serum screening

Important considerations about prenatal screening tests

Screening tests can determine who is at increased risk o having a baby with Downsyndrome. Women choosing screening tests should be inormed that they will beoered urther testing i they have an increased risk and that they may choose toproceed to diagnostic testing. Reasons or not having diagnostic testing includeconcern about the risk o miscarriage, not wishing to know prior to the birth, and

termination o pregnancy being unacceptable to the amily.

Screening tests are non-invasive so there is no increased risk o miscarriage romthe procedure.

Every screening test has a alse positive rate, where women receive an increased riskresult even though their baby is unaected. This rate is usually around 5%.

In the majority o pregnancies with an increased risk result on a screening test, thebaby is unaected. A common misconception held by women is that screening testsshow that the etus has Down syndrome. Anxiety at any increased risk result is normal(see, Genetics in practice).

Low risk results do not exclude Down syndrome or other abnormalities.

A second trimester ultrasound may detect some birth deects but is not recommendedas a screening test or Down syndrome. Neural tube deects and some other conditions may also be detected with second

trimester maternal serum screening.


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Ultrasound scanning

Ultrasound scans are screening tests or some birth deects, with varying degrees o accuracy dependingon the condition.

Ultrasound scans can be a diagnostic tool or some birth deects (eg neural tube deects). Ultrasound scans are non-invasive, and current evidence supports that they pose no threat to the baby.

Ultrasound screening or etal anomaly should not be considered a routine test, but should be oered asa choice or all pregnant women.

First trimester ultrasound

Usually between 8 and 11 weeks gestation. Used to: > Conrm gestational age

> Check the pregnancy when there has been a complication such as bleeding

> View the position o the placenta

> Conrm presence o multiple pregnancy

> Check etal growth, physical development and viability

Second trimester ultrasound

Usually at 18 to 20 weeks gestation. This ultrasound or etal anomaly should not be considered a routine test, but should be oered as a choiceor all pregnant women.

May be used to detect: > Neural tube deects (anencephaly, spina bida)

> Cardiac deects

> Gastrointestinal malormations (gastroschisis, exomphalos)

> Limb deects

> Central nervous system deects

> Urinary tract anomalies

> Sot signs that may be associated with underlying chromosomal or other genetic conditions

Figure 3. First trimester ultrasound



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Limitations o second trimester ultrasound

Not all malormations can be detected by ultrasound at a second trimester etal anomaly scan(18 to 20 weeks). The sensitivity depends on many actors including the:

> Nature o the malormation

> Experience o the operator

> Position o the placenta

> Maternal weight (obesity)

> Resolution o the ultrasound equipment

Visualisation o the etus can be aected by actors such as the womans build and the position andsize o the etus.

Second trimester ultrasound scan is not recommended as a primary screening test or Downsyndrome.

The signicance o changes (sot signs o chromosome abnormality) detected by ultrasound may bedicult to interpret. Further investigations may be indicated. Advice can be sought rom a specialistultrasonographer, Genetics Services or an obstetrician in a high-risk pregnancy management unit.

Ultrasound and neural tube deects

The best detection method or neural tube deects is an ultrasound scan during the second trimester(18 to 20 weeks).

I a previous pregnancy has been aected by a neural tube deect or there is a 1o relativewith a neural tube deect, a specialised ultrasound scan at both 12 to 13 weeks or anencephaly and18 weeks or other neural tube deects, is recommended.

The identication o a neural tube deect by ultrasound depends on the skill o the operator,the equipment, the position and gestation o the etus, and maternal conditions.

Figure 4. Second trimester ultrasound


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Nuchal translucency screening

Nuchal translucency (NT) describes the appearance o a fuid-lled space at the back o the etalneck that can be seen using ultrasound early in pregnancy. The depth o the fuid in this space canbe measured using ultrasound. The thicker the nuchal translucency the greater the risk o etalanomalies such as Down syndrome, other chromosomal conditions, cardiac deects and some raregenetic conditions (see Chromosomal conditions)

NT measurements should only be perormed by trained and accredited operators, using a riskassessment program that incorporates NT, Crown-Rump Length (CRL) and maternal age. This testshould be done when the etus has a CRL o 45 to 84mm, which corresponds to the period11 weeks 3 days to 13 weeks 6 days.

It should be noted that nuchal translucency screening alone is not recommended as ascreening test or Down syndrome and that it should be combined with a biochemicaltest (see below Combined frst trimester screening) i available.

Combined irst trimester screening

It is recommended that the NT screening test be done in conjunction with a maternal blood test.Two proteins present in the maternal blood are measured. These are PAPP-A (pregnancy associatedplasma protein) and ree -subunit o human chorionic gonadotrophin (ree -hCG). Levels o theseproteins vary, but tend to be dierent in women who are carrying etuses with Down syndrome ortrisomy 18. Increased ree -hCG with decreased PAPP-A is suggestive o Down syndrome, while decreasedlevels o both analytes is suggestive o trisomy 18.

By having the blood test in combination with the NT screening test, around 85-90% o babies who haveDown syndrome and occasionally other problems will be picked up, compared to 70% or less using NTon its own.

Approximately 5% o combined rst trimester screening tests give an increased risk result. This gure variesdepending on maternal age. Women with an increased risk result should be oered a diagnostic test. Themajority o increased risk results are not due to Down syndrome, and most o these babies will be healthy.

Results are usually available on the day o the NT ultrasound, i blood was collected prior to the ultrasoundat 10 to 12 weeks gestation, although this will depend on the local provider.

Results are provided as risks or Down syndrome and the other chromosomal trisomy 18, at the time oscreening 1. Note then that this is not a risk o delivering an aected etus. Approximately 30% o babieswith Down syndrome do not survive to term.

Depending on the State/Territory, combined rst trimester screening is not always available in the publicsector, and there may be out-o-pocket costs or the patient (reer to Table 1).

1 However, in Western Australia the risk gure is adjusted to give the risk at the time o delivery.

Figure 5. First trimester ultrasound showing nuchal translucency

nuchal translucency


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Arranging combined frst trimester screening

Tests should be arranged a couple o weeks in advance to allow time to coordinate the blood test andultrasound. The blood test should ideally be perormed rst.

Arrange the ultrasound scan with a Fetal Medicine Foundation (FMF) accredited operator (see Table 1). Arrange the blood collection at an appropriate gestation (see Table 1). Blood can be collected at the local

pathology service but the request should have clear instructions or the sample to go to the screening lab.

This process varies between States, private and public sectors, and metropolitan and regional centres.For specic details regarding co-ordinating the results o the blood and nuchal translucency test contactyour local FMF accredited operator o choice.

Thefactorsthatneedtobeenteredintotheriskcalculationalgorithmshouldbenotedontherequestformincluding:

LMP & EDD Current weight Maternal age Previous child with a chromosomal abnormality Date and location o ultrasound scan a

Any other inormation requested on the orm, eg ethnicity, IVF detailsa I the results o the scan are not received by the date on the orm, the laboratory will contact the

ultrasound practice or the requesting doctor.

Second trimester maternal serum screening

The optimal time to have this test perormed is between 15 and 17 weeks, but it can be perormed until20 weeks.

Second trimester maternal serum screening uses a blood test in conjunction with the maternal age,gestational age and maternal weight to calculate a risk gure or Down syndrome. This screening test mayalso detect pregnancies with an increased risk or trisomy 18 (see Chromosomal conditions) and neuraltube deects.

Maternal blood contains hormones and proteins produced by the etus and placenta, including alpha-etoprotein (AFP), unconjugated estriol (E3), ree -subunit o human chorionic gonadotrophin(ree -hCG), and inhibin A.

Levels tend to be altered in pregnancies aected by Down syndrome, trisomy 18 or neural tube deects. InDown syndrome, the levels o AFP and E3 tend to be reduced, and ree -hCG and inhibin A increased. Inneural tube deects AFP may be increased and, in trisomy 18, levels o all these substances are decreased.

The number and type o analytes used may vary between pathology services. The quadruple test measuresour analytes (AFP, E3, ree -hCG and inhibin A), whilst the triple test measures three analytes. Detection

rates are improved when our analytes are used. Using the quadruple test with ultrasound dating: > 75% o etuses with Down syndrome are detected by second trimester maternal serum screening,

and approximately 5% o tests give an increased risk result. Women aged 40 and over have higherdetection rates, with 95% o aected pregnancies receiving an increased risk result. At least 50% oall women in this age group will receive an increased risk result.

> 85% o babies with a neural tube deect will be detected using maternal serum screening alone.When combined with a detailed ultrasound, the detection rate or spina bida can be as high as 95%,and 100% or anencephaly.

Results are usually available within 24 to 48 hours o collection, but may take longer in parts o regionalAustralia. Women at increased risk are oered diagnostic testing. The majority o increased risk results are

not due to Down syndrome and most o these babies are unaected . The possibility o alse positiveresults and the management options should be discussed with women prior to screening, as should theact that this blood test cannot denitively identiy babies with Down syndrome, trisomy 18, or neuraltube deects.


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Arranging second trimester maternal serum screening

Thefactorsthatneedtobeenteredintotheriskcalculationalgorithmshouldbenotedontherequestform:

Ultrasound-based gestation or LMP

Current weight

Maternal age Previous child with a chromosomal abnormality as well as previous child or close

relative with a neural tube deect

Date o collection I the woman has insulin-dependent diabetes And any other inormation requested on the orm, eg ethnicity, IVF details

Some States and Territories Antenatal Screening Programs receive government unding to perorm thistesting on public patients, and so there is no out-o-pocket cost.

For private patients, the cost depends on the pathology provider. This test does not need to be repeated unless blood was collected at less than 14 weeks gestation.

Counselling or an increased risk result

Cut-o risks are chosen to decide who is at an increased risk as a result o screening. Women at increasedrisk can then be oered diagnostic testing. Cut-o risks or trisomy 18 and Down syndrome are listedbelow. For neural tube deects an AFP level is measured in MoM (multiple o the population median,corrected or gestation). Note that there is some State variation.

Table 3. Cut-o risks used to determine increased risk in prenatal screening

Screen DownSyndrome Trisomy18 Neuraltubedefect

Combined rst trimester screening 1 in 300 1 in 300 a

Second trimester maternal serum screening 1 in 300 a 1 in 300 b 2MoM c

a Cut-o in Victoria is 1 in 250b Cut-o in Victoria is 1 in 200, cut-o in NSW is 1 in 250c Cut-o in Victoria is 2.5MoM

First conrm the gestational age as incorrect gestational age estimation can aect accuracy o results. It may be helpul to discuss the results with the service provider prior to inorming the woman/couple. Listen and give the woman/couple time to absorb the news, consider available options and to make

decisions about urther testing. Inormed decision-making is assisted by the provision o up-to-date,unbiased inormation.

Ensure the woman understands that while the pregnancy is at increased risk or the condition, the resultis not denitive.

A common misconception held by women is that screening tests show the etus has Down syndrome.It can take some listening, clarication and explanation to counteract this belie. Anxiety at any increased riskresult is normal (see Genetics in practice).

Reassure the woman that the majority o babies with an increased risk result will be normal and healthy. Discuss the option o diagnostic testing. Not all women decide to proceed to diagnostic testing. Reasons or

not having diagnostic testing include concern about the risk o miscarriage, not wishing to know prior to thebirth, and termination o pregnancy being unacceptable.

> Post-test counselling is available rom specialist obstetricians and Genetics Services. Reerral shouldbe considered or discussion o diagnostic tests and counselling or women with increased anxiety


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Ways o explaining prenatal screening risk fgures

Giving an increased risk result:A 29 year old woman receives an increased risk result or Down syndrome ater aserum screen test. The risk is 1 in 100. Prior to the test her risk was based on maternalage alone and was 1 in 1002.

Comparison to other women getting the same test result:

O 100 women with this test result, on average, one will have a baby with Downsyndrome and 99 will have babies who do not have Down syndrome.

Risk relative to maternal age:Your risk is now similar to that o a 39 to 40 year old who has not had anyscreening. Women who have this level o risk are oered urther testing todetermine i the baby has Down syndrome.

Prenatal diagnostic tests

Types o prenatal diagnostic tests include: > Chorionic villus sampling (CVS)

> Amniocentesis

> Ultrasound

Important considerations about prenatal diagnostic tests

CVS and amniocentesis testing require invasive sampling procedures to obtain cells orchromosome analysis or specic genetic tests.

It is not possible to detect or diagnose every possible condition a child might have using

prenatal diagnosis. Both CVS and amniocentesis have a risk o miscarriage. The risk is operator dependent,

so tests should be perormed by an experienced operator.

Indications or oering diagnostic testing include: > Advanced maternal age (37 yr in Victoria, 35 yr elsewhere)

> A previous pregnancy with a chromosome abnormality

> The presence o sot signs o chromosome abnormality during ultrasound examination

> A parent carrying a chromosome translocation (5% o Down syndrome is caused byan unbalanced translocation involving chromosome 21 that was inherited rom aparent with a balanced orm o the translocation, see Chromosomal conditions)

> An increased risk result on a screening test > An increased risk o having a baby with a genetic condition usually when there is a

amily history o an inherited genetic condition

Prior to testing, there should be a ull discussion o the advantages and disadvantageso the procedures, the implications o the possible test results and subsequentmanagement options, including methods o termination o pregnancy and the availablesupports.


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Transabdominal aspiration otissue

Villi o chorionrondosum

Transvaginal aspirationo tissue

Ultrasoundtransducer

Chorionic villus sampling (CVS)

This procedure is usually perormed rom 11 weeks, routinely between 11 and 13 weeks gestation 2.It should not be perormed prior to 10 weeks gestation due to the risk o limb deects.

A sample o chorionic villus (pre-placental tissue) is removed by a ne needle, either transabdominally,or less requently transvaginally, under ultrasound guidance (see Figure 6).

The tissue is used or chromosome analysis, and in some specic situations, may be used or diagnosis(DNA or biochemical analysis) o a genetic condition where there is a amily history.

It is a procedure that can be perormed earlier in pregnancy than amniocentesis, and has the benets o anearly scan that may detect anencephaly.

Some women experience cramping and, occasionally, vaginal bleeding ater CVS. The miscarriage rate, in experienced hands, is estimated at ~1% above the background risk.2 In South Australia CVS is sometimes perormed between 10 and 11 weeks

Important points about CVS

CVS has a 1% risk o equivocal results. This includes the risk o placental mosaicism the presence o a

mixture o cells with normal and abnormal karyotype, or maternal cell contamination o the sample. In thiscase, amniocentesis may be necessary to clariy the karyotype o the etus.

CVS has a 0.1% rate o ailure to detect a pregnancy with a chromosomal anomaly, due to the occasionswhen there is an abnormal karyotype in the baby, but not in the placenta.

CVS may not detect etal chromosomal mosaicism. Test results take about one week.

Figure 6. CVS procedure


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Amniocentesis

The procedure is perormed rom 15 weeks routinely, to approximately 19 to 20 week gestation. A sample o amniotic fuid is removed rom around the etus by a ne needle, under ultrasound guidance

(see Figure 7).

Testing is perormed on amniotic fuid cells, most o which originate rom the etus, compared with CVS,where placental cells are tested.

Test results take between one and three weeks. Discomort is usually minimal, though a very small number o women experience pain as the needle

passes through the peritoneum.

The miscarriage rate is lower than that or CVS and estimated to be around 0.5% above the backgroundrisk in experienced hands.

Amniocentesis may not detect mosaicism, because o the limited number o cells counted in a routine test. As amniocentesis is a second trimester test, the pregnancy is more advanced when results become

available, compared with CVS.

NB: amniocentesis is not the preerred screening test or neural tube deects. An ultrasound at 18 to 20weeks gestation is more accurate.

Arranging CVS and amniocentesis

Reer to a private ultrasound practice or public hospital ultrasound department. The womans blood group should be given on the request orm, as rhesus negative women will require an

anti-D injection.

There are no out-o-pocket costs in the public system i there is an indication or testing. For private patients, there are costs or both the sampling procedure and chromosome analysis. Contact

service providers or details listed at the end o this section.

Figure 7. Amniocentesis

Transabdominalaspiration o fuid

Amniotic fuid

Ultrasound transducer


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Ultrasound diagnostic testing

May be used to detect: > Neural tube deects (anencephaly, spina bida)

> Cardiac deects

> Gastrointestinal malormations (gastroschisis, exomphalos)

> Limb deects > Central nervous system deects

> Urinary tract anomalies

> Sot signs that may be associated with underlying chromosomal or other genetic conditions

Genetic testing

Chromosome analysis

Prenatal diagnostic testing involves etal or placental cells being examined to look at the number andstructure o each chromosome. A ull chromosome analysis, called a karyotype, allows the diagnosiso chromosomal abnormalities. A karyotype takes 7 to 14 days and the result will be sent to the

reerring clinician. Where there are strong indications o a etal anomaly (eg a markedly increased risk screening result),

or where a preliminary result is required quickly, FISH (fuorescent in situ hybridisation) analysis mayalso be perormed on samples obtained using CVS or amniocentesis. FISH results may be availablein 1 to 2 days.

Indications or FISH:

Fetal anomaly detected on routine second trimester ultrasound scan. Markedly increased risk result on a screening test.

Late gestation. Parental anxiety. Benefts o FISH:

Provides a quick preliminary result or the presence o Down syndrome and certain otherchromosome trisomies within 24 to 72 hours.

FISH will detect chromosome abnormalities. The number o probes used will determine thetype o chromosome abnormalities detected.

> Three-probe FISH will detect Down syndrome and sex chromosome abnormalities

> Five-probe FISH will detect Down syndrome, trisomy 18, trisomy 13 and sex chromosomeabnormalities

The limitations o FISH

FISH can give alse positive results, and thus an abnormal result needs to be interpretedcautiously i other indications o trisomy are not present.

FISH can give alse negative results. A normal FISH result only excludes ull trisomies o thechromosomes tested (usually 13, 18, 21, X, Y). FISH usually cannot rule out structuralabnormalities o these chromosomes, nor trisomies o other chromosomes.

FISH does not replace a complete chromosome analysis (karyotype) and this should still becompleted.

FISH results may be inconclusive i both normal and abnormal cells are present (mosaicism).


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Arranging a FISH test

FISH is requested by the obstetrician or the ultrasonographer. There is no Medicare rebate or FISH. The charge or FISH depends on the laboratory doing the testing and the number o probes used. Costs or three-probe FISH may be less than or ve-probe FISH.

Contact the pathology or ultrasound service or details o costs.

Results are usually available in 24 to 72 hours.

Genetic conditions requiring DNA testing

A woman/couple with a amily history o a genetic condition must be reerred to Genetics Services assoon as possible, preerably prior to pregnancy.

Testing or inherited conditions (eg cystic brosis or thalassaemia) requires knowledge o the causativegenetic mutation in the amily. This may require extensive, time-consuming tests beore a prenatal test canbe oered. Reerral once the woman is pregnant may be too late to oer prenatal diagnosis.

In cases o rarer conditions the laboratory may need to be notied in advance. Some tests are onlyavailable interstate or even overseas, and much co-ordination is needed or shipping and testing to ensure

a timely result.

Seehttp://hgsa.com.au/images/UserFiles/Attachments/HGSALaboratories06Aug.pd(pages 5 to 8)or a list o genetic tests available.

CVS is the preerred diagnostic procedure when a pregnancy is known to be at increased risk o a geneticcondition. Prenatal diagnosis o genetic conditions requires the coordination o the sampling procedure,cytogenetic laboratory and DNA laboratory. The woman/couple should thereore be reerred to GeneticsServices as soon as the pregnancy is conrmed. The time until results are available will depend upon thetype o test perormed.

Pre-implantation genetic diagnosis (PGD)

PGD is the genetic testing o embryos prior to implantation in the womb and relies on usual IVF techniquesto generate embryos in vitro. Embryos are usually tested at day 3 (6 - 10 cells) ater ertilisation.I ertilisation using conventional IVF is unsuccessul, ICSI (Intra Cytoplasmic Sperm Injection) technologymay be used.

> As shown below, pre-implantation genetic diagnosis uses assisted reproduction technology (ART).Hormones are used to stimulate a woman's ovaries and enable the collection o a number o eggs oroocytes. Ater the eggs are removed, the eggs are ertilised in the laboratory with sperm. Those eggsthat are successully ertilised are allowed to divide and multiply or 3-6 days, by which stage theycontain about 8 cells or have developed into a blastocyst. Not all ertilised eggs make it to this stage.

> One or two cells are removed in order to test or the specic genetic condition in question. Theremoval o these cells does not appear to harm the developing embryo. Only those embryos that donot appear to be aected will be transplanted into the mother's uterus usually on the same day.

Generally, no more than one or two embryos will be transerred to the uterus at any one time toavoid the possibility o multiple births. In some IVF centres, unaected embryos that are not used canbe rozen or transer in another cycle.

The PGD process

Tests that can be perormed

Identication o sex or diagnostic reasons but not or amily balancing. FISH analysis to identiy chromosome trisomies and translocations. DNA testing or selected single gene conditions. Testing can only be perormed i the gene mutation(s) causing the condition are known and

testing or the mutation(s) is accurate on a single cell.


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Advantages o PGD

I a woman and her partner are trying to avoid a pregnancy aected with a certain geneticcondition, the risk o this can be minimised without termination o the pregnancy.

Reerral or specialised counselling is required. This provides a orum to discuss issues in detailwith an experienced counsellor who has been trained in this area.

Figure 8. Pre-implantation genetic diagnosis

Fertilised using IVFtechniques

Post ertilisation(day 3-6 depending

on laboratory)

Remove one or two cells or testing

SpermEgg

Test resultTest DNA orchromosomes

Genetic conditionexcluded

Genetic conditiondetected

Embryo nottranserred

Embryotranserred

Limitations o PGD

There is no guarantee o achieving a pregnancy. Most couples undergo several cycles otreatment beore achieving an ongoing pregnancy.

Accuracy is high, but not 100%. The woman must undergo IVF procedures. The procedures and testing are expensive. It is time consuming and requires meticulous lab work. There is a risk o multiple pregnancy i more than one embryo is implanted.

Counselling issues

Risks and success rates o PGD must be made clear in relation to other methods o avoidinggenetic risk.

There can be personal moral dilemmas regarding the use o embryos not implanted. Grie and loss. Attitude to prenatal diagnosis


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Managing a pregnancy with an abnormal karyotype

(See also Genetics in practice.)

It may be helpul to discuss the results with the service provider or clinical geneticist prior to inorming thewoman/couple.

Pre-test counselling should prepare the woman/couple or the possibility o a chromosome abnormalitywhich may not have been anticipated.

Listen and give the woman/couple time to absorb the news and consider their options. Reerral to specialist Genetics Services is recommended or sex chromosome abnormalities and mosaic

results and should be considered or all other abnormal karyotypes.

Not all chromosome abnormalities have a major eect on the baby. Medical texts are oten out o date.It is important that the woman/couple receives up-to-date, unbiased inormation about the potential eectso a chromosome abnormality. Discussion with support groups can be helpul or parents (see Contacts,support and testing).

Decisions regarding the pregnancy should only be made once there has been a ull discussion o theimplications o the test results and the management options. This might include reerral to GeneticsServices, discussion with obstetricians and paediatricians, and reerral to the relevant support group (see

Contacts, support and testing).

Managing a pregnancy with a etal anomaly

Reerral o public patients to a high-risk clinic, perinatal management unit or etal diagnostic unit is stronglyrecommended or a management plan and coordination o ongoing care. Further prenatal testing may beneeded to clariy the diagnosis, eg abdominal wall deect may be due to a chromosomal trisomy.

Pre-test counselling should prepare the woman/couple or the possibility o a structural abnormality whichmay be detected incidentally.

Women and amilies can benet rom detailed discussion with support groups. The Fetal Medicine orGenetics Services will usually arrange or the amily to meet clinicians who have experience in themanagement o babies with disability and birth deects. These services are located in the public and

private sector. A management plan may include providing the couple with: > The opportunity or consultation with appropriate specialists

> Further diagnostic procedures

> Further ultrasound scans in the presence o the appropriate clinical specialist (eg cardiologist presenti cardiac deect is suspected)

> Genetic counselling

> Ongoing support i the pregnancy continues to term

> Specic plans or delivery, postnatal care and support

> Contact details o the relevant support groups


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Counselling regarding termination o pregnancy

It is common or women/couples to be deeply shocked ater receiving dicult/bad news. They otenimmediately request a termination. It is important to allow some time or the woman/couple to cometo terms with the news and consider their decision. This may include discussions with relevant healthproessionals and support groups.

I termination o pregnancy is an option, the woman/couple should be encouraged to make their decision

based on their personal values and accurate, up-to-date and unbiased inormation. When women/couples have a choice o the method o termination, all options and the associated risks

and advantages should be discussed, preerably with an obstetrician or prenatal Genetics Services.

Whether or not they wish to see the baby ater termination should be discussed in advance. I a post-mortem examination is required or accurate diagnosis, this should also be discussed in advance. Grie ater a termination is a normal reaction to the loss o a wanted pregnancy and can be complicated

by eelings o guilt and anxiety or uture pregnancies.

Ongoing support or the woman/couple is important, regardless o their decision. Women/couples mayturn to their GP or support, or benet rom consultation with a genetic counsellor with experience inprenatal diagnosis. Contact your local AGA Peak Body (see Contacts, support and testing) or a localsupport group.

Management o a pregnancy identifed as increased risk by screening,but ound to have a normal etal karyotype

The woman/couple will experience a raised level o anxiety, even with the best counselling support. Ater a diagnostic test (such as CVS or amniocentesis ollowed by karyotyping) excludes a chromosomal

condition (Down syndrome, trisomy 18 or 13), the pregnancy remains at increased risk o other etalanomalies or obstetric complications.

All women with increased risk ollowing screening tests, but normal etal karyotypes, should be reerred oran 18 to 20 week detailed morphology ultrasound, and be monitored closely throughout the remaindero the pregnancy.


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Frequently asked questionsWhat i the woman presents late?

A woman who is not at increased or high risk o having a baby with Down syndrome and rst presentsater 20 weeks gestation is limited to an ultrasound scan or etal anomalies, which should be immediatelyarranged.

For a woman aged 35 years and over (or 37 in Victoria) at EDD, an amniocentesis with FISH could be

considered up to the end o the 20th week, although terminations o pregnancy are usually required to bedone at less than 2022 weeks. This may vary in dierent States and Territories according to their laws.

FISH analysis could be perormed to give a preliminary result within 48 hours o the amniocentesis, with thenal karyotype result taking up to two weeks. The pregnancy is then airly advanced and termination opregnancy may not be available as an option.

What do I say to a woman who is anxious while waiting or her results?From the time the test is arranged, it is important that the woman be given accurate inormation and realisticexpectations, including the maximum period to wait or test results. She should be inormed that the timetaken to receive results does not indicate i they will be normal or not. Talking about the most likely outcomescan be helpul, but avoid alse reassurance. Oten listening to the womans anxieties and using counsellingskills such as active listening, normalising and acknowledging the distress and uncertainty are useul. Makeinormation available upon request.

What do I do i a woman says there is something abnormal on a test result but I havent receivedthem yet?

Contact the laboratory that conducts the test to clariy the situation.

What do I say to a woman whose Down syndrome risk has increased, but is still below thecut-o or a diagnostic procedure?

Explore the meaning o this result or the woman. While her risk is greater than other women her age, her risko having a baby with Down syndrome is still low. Some women may not be prepared to accept a certain levelo risk and may still choose to have a diagnostic test.

Can a woman have both frst and second trimester screening tests?Intuitively, more screening will identiy abnormalities better however this does not occur in practice. For amarginal increased detection rate or Down syndrome, the alse positive rate will rise substantially. I a womanhas both screening tests, she is more likely to be identied at increased risk, and oered an invasive diagnosticprocedure. The more invasive procedures perormed, the greater the risk o causing spontaneous loss o anunaected etus. Thereore, it is strongly recommended not to have both rst and second trimester screening tests.


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Correcting misunderstandings

Im young, so I dont need to have any tests or Down syndromeAlthough younger women are at lower risk than older women, many babies with Down syndrome are stillconceived by women who would not be dened as at increased risk due to their age (ie 35 or 37 years andabove). Screening tests should be oered to women o all ages.

Diagnostic testing can ollow i requested.

The tests were all OK, so my baby is normalTests during pregnancy can detect increased risk or presence o certain conditions only. No test, orcombination o tests, will detect all birth deects or medical conditions.

My blood test was normal, so my baby doesnt have Down syndromeBlood/screening tests cannot detect all pregnancies with Down syndrome. A woman with a normal (low risk)screening test result does have a chance o having a baby with Down syndrome but this risk is not highenough or diagnostic testing to be indicated.

The blood test says theres something wrong with my baby

Blood/screening tests during pregnancy do not detect birth deects; they indicate which pregnancies have anincreased risk o certain genetic conditions and birth deects. Most etuses with abnormal (increased risk) testresults do not have Down syndrome. This is an indication or reerral or diagnostic procedures.

The blood test says there is something wrong so I need a diagnostic testI the blood/screening test was second trimester maternal serum screening, increased risk results are due toinaccurate dates (i LMP only given) in 30% o cases. Check dates by ultrasound. An increased risk result ona screening test is an indication or diagnostic testing; however, a small number o women choose not to havediagnostic testing.

I I have another screening test, I might get a better resultScreening tests are most accurate when done at the correct time in the pregnancy. Retesting is only

perormed i dates are inaccurate. It is strongly recommended not to have both rst and second trimesterscreening tests (see above, Frequently asked questions).

I am over 35 years so I need to have a CVS or amniocentesisWomen aged 35 years and over (or 37 years in Victoria) at EDD may choose to have a diagnostic test, maypreer the option o screening tests, or may choose to have no tests at all. Women in this age group should beaware that they are more likely to have an increased risk result rom a screening test as age is part o the riskcalculation, in which case they will then need to consider diagnostic testing.

Its not worth having any tests because I wouldnt terminate the pregnancySome people eel it is benecial to know i the etus has an anomaly to prepare or the birth and uture.Others preer to wait until delivery. All women should have the opportunity to consider testing.


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List of fetal medicine services in public hospitalsassociated with the state genetics services in Australia

AustralianCapitalTerritory

The Canberra Hospital Genetic Counsellor, PO Box 11, WodenACT 2605

Ph: (02) 6244 2133Fax: (02) 6244 4625

NewSouthWales

Camperdown Royal Prince Alred Hospital Department o Molecular and Clinical Genetics,Building 65, Level 6 Missenden Road, CamperdownNSW 2050

Ph: (02) 9515 5080Fax: (02) 9550 5389

Kogarah St George Hospital Women and Childrens Health

Gray Street, KogarahNSW 2217

Ph: (02) 9113 3635Fax: (02) 9113 3694

Liverpool Liverpool Hospital Fetal Medicine UnitLocked Bag 7103, Liverpool BCNSW 1871

Ph: (02) 9828 5631Fax: (02) 9828 5570

Newcastle John Hunter Hospital Maternal and Fetal MedicineLocked Bag 1, Hunter Region Mail Centre, NewcastleNSW 2310

Ph: (02) 4921 4694Fax: (02) 4921 3133

Penrith Nepean Hospital Perinatal UltrasoundLevel 3 South Block, Derby Street, PenrithNSW 2751

Ph: (02) 4734 2578Fax: (02) 4737 3206

Randwick Royal Hospital or Women Maternal/Fetal MedicineBarker Street, Randwick

NSW 2031Ph: (02) 9382 6098Fax: (02) 9382 6706

St Leonards Royal North Shore Hospital Fetal Medicine UnitPacic Highway, St LeonardsNSW 2065

Ph: (02) 9926 6478Fax: (02) 9926 7880

Westmead The Childrens Hospital Department o Clinical GeneticsLocked Bag 4001, Westmead

NSW 2145Ph: (02) 9845 3273Fax: (02) 9845 3204


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NorthernTerritory

There is currently no clinicalgenetics service or outreachservice available in theNorthern Territory

Queensland

Royal Brisbane Women'sHospital

Antenatal ClinicCnr Bowen Bridge & Buttereld Rds, HerstonQld 4029

Ph: (07) 3636 2269Fax: (07) 3636 5379

Mater Mother's Hospital Raymond Terrace, South BrisbaneQld 4101

Ph: (07) 3840 1593Fax: (07) 3840 1621

SouthAustralia

Womens and ChildrensHospital

South Australian Clinical Genetics ServiceYouth and Womens Health Service, North AdelaideSA 5006

Ph: (08) 8161 7375Fax: (08) 8161 6088

Antenatal Diagnosis andCounselling Service

Department o Obstetrics and GynaecologyWomens and Childrens HospitalSouth Australian Clinical Genetics Service72 King William Road, North Adelaide

SA 5006Ph: (08) 8161 7633Fax: (08) 8161 7654

Perinatal DysmorphologyGroup

Department o Obstetrics and GynaecologyFlinders Medical Centre, Bedord ParkSA 5042

Ph: (08) 8204 4577Fax: (08) 8204 3143

Tasmania

Royal Hobart Hospital Tasmanian Clinical Genetics ServiceGPO Box 1061L, HobartTas 7001

Ph: (03) 6222 8296Fax: (03) 6222 7961


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Victoria

Genetic Health ServicesVictoria (GHSV)

Clinics are conducted in 10metropolitan and 11 ruraland regional centres

10th Floor, Royal Childrens HospitalFlemington Road, ParkvilleVic 3052

Ph: (03) 8341 6270Fax: (03) 8341 6390

Monash Medical Centre Monash Medical Centre246 Clayton Road, ClaytonVic 3168

Ph: (03) 9594 2026Fax: (03) 9594 6022

Royal Womens Hospital Specialty Genetics Services132 Grattan Street, CarltonVic 3053

Ph: (03) 9344 2121Fax: (03) 9344 2066

WesternAustralia

King Edward MemorialHospital or Women

Fetal Medicine Service374 Bagot Road, SubiacoWA 6008

Ph: (08) 9340 1525Fax: (08) 9340 1678

BibliographyBarlow-Stewart K, 2004. Prenatal Testing: Special Tests For Your Baby During Pregnancy. In The AustralasianGenetics Resource Book (Ed Barlow-Stewart K), Centre or Genetics Education, Royal North Shore Hospital,Sydney NSW ISBN 0-9580797-2-2. Accessible athttp://www.genetics.com.au

Ga C, Newstead J and Metcale S, 2003. Testing during pregnancy. In The Genetics File. Victorian Departmento Human Services, Melbourne ISBN 0 7311 61777http://www.mcri.edu.au/GF/pages/GeneticsFile.asp

Gardner, RJ and Sutherland GR, 2004. Chromosome abnormalities and genetic counselling,Oxord University Press.

The Royal Australian and New Zealand College o Obstetricians and Gynaecologists. www.ranzcog.edu.auAccessed September 2006.

Further inormationFor inormation regarding prenatal testing during pregnancy translated into Arabic, Chinese, English, Farsi,Japanese, Korean, Thai, Vietnamesehttp://www.mhcs.health.nsw.gov.au/mhcs/topics/Pregnancy_and_Post_Natal.html

Scroll down the list to nd Prenatal Testing Special tests or your baby during pregnancy.


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Contacts and further information All states and the ACT have amilial cancer services. Contact them through your local state

or territory health department.

Pregnancy and alcohol at http://www.alcoholguidelines.gov.au How diet can prevent birth deects. Available in Arabic, Chinese, Croatian, English, Italian,

Khmer/Cambodian, Korean, Portuguese, Russian, Serbian, Spanish, Thai, Turkish andVietnamese at http://www.mhcs.health.nsw.gov.au/health-public-affairs/mhcs/

publications/3460.html

MyDr at http://www.mydr.com.au The Centre or Genetics Education at http://www.genetics.edu.au HealthInsite at http://www.healthinsite.com MedicineNet at http://www.medicinenet.com

For other related act sheets, you can contact the Gene Technology Inormation Serviceon freecallAustralia-wide1800631276or email [email protected] visit Biotechnology Australia's website at http://www.biotechnology.gov.au



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Testing if you are pregnant

Most children born in Australia are born healthy. But about 2 or 3 in 100 are born with a conditionthat means they will need medical care.

Some o the more common conditions are:

Congenital heart disease Disorders o the kidney and bladder Hip dislocation at birth

Club oot Down syndrome and other chromosome alterations Spina bida and related conditions, which are known as neural tube deects and which are

problems in the development o the spinal cord and/or brain

Clet lip and/or palate Developmental delay.

Some o these can be detected in pregnancy, while others cannot.

Screening tests and/or diagnostic tests are available or some o these disorders. They are not

compulsory it is your choice whether or not to have these tests.

Beore having any tests, you need to consider what you would do i a test came back positive orindicates some degree o risk. What would you do i a test showed your unborn child had anabnormality? Would you consider a termination o pregnancy? Would you not consider one? Wouldyou just like to know, even i you dont plan to do anything about it? Or would you rather not know?

Screening testsThese tests do not give a rm diagnosis, but aim to give parents an idea o whether or not theyhave a higher than normal risk o having a child with the disorder being screened or.

None are perect sometimes screening tests miss the conditions they are meant to detect.

I a screening test picks up an increased risk, then there are diagnostic tests chorionic villus sampling,amniocentesis or ultrasound that can sort out whether or not the baby has the disorder.

Patient and family fact sheet



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First trimester screening testThis test is designed to identiy women at increased risk o having a baby with Down syndrome, butit can sometimes also identiy other problems.

The test has three parts. The rst is a blood test at 10 to12 weeks o pregnancy. The second is anultrasound, called a nuchal translucency or NT test, at 11 to13 weeks. The third part is the womansage, which is also taken into account.

These three pieces o inormation are combined to calculate the risk that the baby has Downsyndrome. Couples with an increased risk will be oered genetic counselling to consider theirchoices; the choice o whether or not to have a diagnostic test either chorionic villus samplingor amniocentesis to check the babys chromosomes.

Nuchal translucency testNuchal translucency is used to estimate i a baby is at an increased risk o having a chromosomalabnormality. It uses ultrasound to see and measure a fuid lled sac at the back o the unbornbaby's neck during early pregnancy.

The nuchal translucency test, which is part o the rst trimester screening test, can sometimes be doneon its own, without the blood test. This ultrasound is carried out between 11 and 13 weeks opregnancy and is reasonably accurate, but not as accurate as the combined rst trimester screening test.

Second trimester maternal serum screening testThis blood test is best done between 15 and 17 weeks o pregnancy, but it can be carried outbetween 14 and 20 weeks. The second trimester screening test is suitable or women who did nothave either the rst trimester screening test or the nuchal translucency test. It can tell parents whetherthe baby is at increased risk o Down syndrome (and/or some other chromosomal alterations) or aneural tube deect, which is a problem in the development o the spinal cord and/or brain.

The second trimester test is not as accurate as the rst trimester screening test.

UltrasoundMost pregnant women will have an ultrasound at 18 to 20 weeks. This ultrasound checks the babysgrowth, the stage o pregnancy, and the amount o amniotic fuid, the position o the baby andplacenta. This ultrasound also looks or physical problems such as neural tube deects, heart andkidney malormations, clet lip and limb abnormalities.

Diagnostic testsThese tests aim to give a rm diagnosis o a potential problem. They are more accurate than screeningtests. Like all tests, they are only looking or specic gene alterations or chromosome alterations (seeact sheet on 'What is a gene?'). They are not perect and they may occasionally miss something.



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Chorionic villus samplingThis test can detect chromosomal alterations as well as genetic conditions, which your doctor knowsto look or because they have happened beore in the amily, or because a genetic screening testhas shown that you could have an aected baby.

Chorionic villus sampling is usually done at around 11 weeks o pregnancy and preerably by 13weeks. Usually, a needle is guided through the abdomen to the tissue that will orm the placenta,and a small ragment o tissue is removed. Occasionally a plastic tube is guided through the vaginaand cervix instead. In both cases, the procedure is monitored by ultrasound so that the needle orplastic tube is kept away rom the baby. Most women nd it uncomortable rather than painul.

Women who have chorionic villus sampling have a slightly increased risk o miscarrying aterwards.The risk is between 1 in 100 and 1 in 200.

The results are usually available in two to three weeks.

AmniocentesisThis test can detect chromosomal alterations. The test can also detect gene alterations, which yourdoctor knows to look or because they have happened beore in the amily, or because a geneticscreening test has shown that you could have an aected baby.

Amniocentesis is usually done at 15 to16 weeks o pregnancy and preerably beore 20 weeks.A needle is guided into the fuid around the baby and a small amount o fuid is removed. Theprocedure is monitored by ultrasound so that the needle is kept away rom the baby. Most womennd it uncomortable rather than painul.

Women who have amniocentesis have a slightly increased risk o miscarrying aterwards. The risk isabout 1 in 200.

The results are usually available in two to three weeks.

UltrasoundA detailed ultrasound may be used to look or certain disorders that have happened beore in theamily. Ultrasound can also be carried out at any time i problems arise in the pregnancy.



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Contacts and further information All states and the ACT have amilial cancer services. Contact them through your local state

or territory health department.

Your local hospital antenatal clinic. MyDr at http://www.mydr.com.au HealthInsite at http://www.healthinsite.com For other related act sheets, you can contact the Gene Technology Inormation Service

on freecallAustralia-wide1800631276or email [email protected] visit Biotechnology Australia's website at http://www.biotechnology.gov.au

03 - testing and pregnancy web

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