Prevention of Birth Defects

An Overview of Primary and Secondary Strategies

Primary Prevention

Single Gene DisordersNo medical intervention available to

correct underlying pathology.Prevention is dependent upon pre-

conceptual genetic counseling of at-risk couples.

Primary PreventionTeratogenic Disorders

Teratogen- any environmental influence that adversely affects the normal development of the fetus

A wide variety measures are available to protect the otherwise healthy fetus from in utero damage.

These include education concerning of the mother concerning nutrition and exposure to teratogenic agents and also

Screening for infectious diseases.

Primary Prevention

Chromosomal DisordersThese disorders are not systematically

predictable and risk factors are not determined.

Aside from pre-conceptual counseling in cases where known risk factors are present primary prevention strategies are not available.

Primary Prevention

Mulifactorial disorders Neural tube defects including spina bifida

were linked to maternal folic acid deficiencies in the early 1990’s.

In 1996 folate supplementation was recommended for women anticipating conception or in the first trimester of pregnancy.

In 1998 folate supplementation was required in grain products produced in the U.S.

Secondary Prevention of Birth Defects

Prenatal Diagnosis

Prenatal Diagnosis

The diagnosis of a disease or a condition in a fetus or embryo before it is born.

The decision as to whether to use prenatal diagnostic procedures is one made as a result of consultation between the family and the care provider. There is no absolute requirement for the utilization of these technologies in any circumstance.

Prenatal Diagnosis

Candidate pregnancies for screening:+ advanced maternal age >35+ previous offspring that were premature or had abnormalities+ chromosomal abnormalities in either parent+ parents at risk for in-born errors of metabolism

+ high levels of maternal serum alpha fetoprotein (AFT)

Prenatal Diagnosis Techniques

Ultrasound

Routinely done around 20 weeks

Detects structural defects

Determines gestational age and sex

No Risk

Prenatal Diagnosis

Transabdominal Amniocentesis

~ 1/4 cup of amniotic fluid removed at 16 wks.

Fluid is produced by fetal lungs, kidneys and umbilical cord. The fluid contains shed fetal skin cells and biochemical substances produced by the fetus.

AFT may indicate neural tube defects

Complication rate: <5%, Miscarriage: .25-.50%

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Prenatal Diagnosis

Chorionic Villi Sampling

Performed at 8-10 wks

Involves passing a small catheter through the vagina into the uterus

Small samples of cells are taken from the placenta, where it attaches to the wall of the uterus.

Miscarriage rate is .5 -1.0%

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