In the Name of God

Obstetrics Study Guide 1

Mitra Ahmad Soltani2008

References

• Pritchard JA, MacDonald PC, Gant NF. Williams Obstetrics. 22nd ed. , NY: McGraw-Hill; 2005

• Lyon D. Use of Vital Statistics in Obstetrics. emedicine. Dec 2007

• RCOG. Electronic Fetal Monitoring. UK.2001

Birth rate

number of births 1000 population

• It includes men in the population.

Fertility Rate

number of live births 1000 women aged 15-44 years

• While a woman with 2 second-trimester miscarriages would be considered fertile, her deliveries would not be included in the fertility rate.

Reproductive Mortality rate

contraceptive use plus direct maternal deaths

100000 women

Maternal Mortality Rate

number of direct or indirect maternal deaths100,000 live births

• A condition in which both mother and fetus are lost would both increase the numerator (maternal death) and decrease the denominator (live birth).

Infant Mortality Rate

infants who die prior to their first birthday 1000 live Births

• IMR is often one of the sentinel indicators used to evaluate a population's overall health and access to health care.

Neonatal Mortality Rate

losses between 0-28 d of life (inclusive) 1000 live births

• This rate is often divided into early (first 7 d) and late (8-28 d) rates.

Fetal Death rate (stillbirth rate)

number of stillbirths 1000 infants (total Births)

• Infants means “live and still” born.

Perinatal Mortality Rate

Fetal deaths+neonatal deaths 1000 total Births

Still birth

• Delivery after 20 weeks' EGA (and more than 500 g birthweight) in which the infant displays no sign of life (gasping, muscular activity, cardiac activity) is considered a stillbirth.

Live Birth

• Delivery after 20 weeks' EGA in which any activity is noted is classified as a live birth. This is a difficult definition, as the lower limit of reasonable viability currently remains around 23 weeks‘ GA. Thus, a spontaneous delivery at 21 weeks‘ GA with reflex motion but no ability to survive with or without intervention would nonetheless be considered a live birth.

Abortion

• The most common definition of an abortion is any loss of a fetus that is less than 20 weeks' completed gestational age (since last menstrual period) or that weighs less than 500 grams.

Preterm Infants

• Preterm infant is another arbitrary definition because a subtle gradient of maturity exists. Premature is defined as a delivery before 37 completed weeks' gestational age, although the vast majority of babies born after 35 weeks' EGA have uncomplicated perinatal courses.

Postterm Infants

• The generally accepted definition of a postterm pregnancy is one that progresses beyond 42 weeks' completed gestational age based on last menstrual period (LMP). In practice, many clinicians use a lower cutoff such as 41 weeks' EGA when LMP is certain.

Uteroplacental blood flow

500 to 700 ml/min

Pelvis Obstetrical conjugate: the shortest AP diameter of inlet, which is

1.5 to 2 cm lesser than the diagonal conjugate. • If diagonal conjugate is >11.5 cm (or OB conjugate >10

cm)we can assume the pelvis inlet is adequate.• If interspinous diameter >10 cm then mid pelvis is assumed

to be normal.• If biischial diameter of the outlet >8 cm then outlet is

adequate.• When the lowermost portion of fetal head is at or below the

ischial spines(it means BPD is passing the inlet) it is usually engaged. Exceptions occur when there is considerable molding, caput formation, or both.

contractions

Braxton Hicks:1-Irregular2-Unpredictable3-Nonrhythmic4-Painless

False labor:1-During The last week or

two of gestation2-Rhythmic3- with discomfort

When corpus luteum is removed before 10 weeks gestation

• Amp 17-hydroxyprogesterone caproate, 150 mg IM

Average weight gain during pregnancy is:

• 12.5 kg(about 25-30 pounds)

Nausea and vomiting in pregnancy

• Commence between the first and second missed menstrual period and continue until about 14 weeks.

4 basic features of fetal heart rate

• Variabilities• Accelerations• Decelerations• Baseline heart rate

Varabilities definitions

• Normal is 5-25 bpm• B-B or short Term V is varying

intervals between successive heart beats .• Long Term v is irregular waves on the

CTG 3-5 bpm.

Factors affecting Baseline variability

• Para-Sympathetic affects short term variability whilst Long Term is more Symp.• CNS ,Drugs reduce Variability• High gestation increases variability

Accelerations• Accelerations are transient increase in FHR of 15

bpm or more lasting for 15 sec.• Absence of accelerations on an otherwise normal

CTG remains un clear. As many as 90 percent of nonreactive tests are false positive.

However:• absence of acceleration with decreased baseline

oscillation of the fetal heart rate(variability)or the presence of late decelerations following spontaneous uterine contractions is consistently associated with uteroplacental insufficiency

Decelerations

• Decelerations are transient slowing of FHR below the baseline level of more than 15 bpm and lasting for 15 seconds Or more.

Early deceleration

Begins on the onset of contraction and returns to baseline as the contraction ends.

Should not be disregarded if they appear early in labor or Antenatal.

Late Decelerations

• Are due to acute and chronic feto-placental vascular insufficiency.

Occurs after the peak and past the length of uterine contraction, often with slow return to the baseline.

Are precipitated by hypoxemia. Associated with respiratory and metabolic

acidosis.

Variable deceleration

• Inconsistent in configuration, No uniform temporal relationship to the onset of

contraction, are variable and occur in isolation.• Worrisome when Rule of 60 is exceeded (i.e. decrease

of 60 bpm,or rate of 60 bpm and longer than 60 sec) • Caused by cord compression of the umbilical cord

Prolonged deceleration

•Drop in FHR of 30 bpm or More lasting for at least 2 min• Is pathological when crosses

2 contractions i.e 3 mins.

Prolonged Decelerations CAUSES

• Cord prolapse.• Maternal hypertension• Uterine Hypertonia• Followed by a Vaginal Examination or

Amniotomy or Spontaneous Rupture of Membranes with High Presenting part.

Management of Prolonged Deceleration

• Maternal position• IV fluids• Vaginal Exam to exclude cord prolapse • Assess BP• FBS if cervix is dilated and well applied to

Presenting part

Baseline tachycardia and Bradycardia

• Uncomplicated baseline tachycardia 161-180 bpm or bradycardia 101-109 do not appear to be associated with poor neonatal outcome.

Causes of baseline bradycardia

Postdates Drugs Idiopathic Arrhythmias Hypothermia Cord compression

Causes of Baseline Tachycardia

Asphyxia Drugs Prematurity Maternal fever Maternal thyrotoxicosis Maternal Anxiety Idiopathic

Sinusoidal Pattern• Regular Oscillation of the Baseline long-term

Variability resembling a Sine wave ,with no B-b Variability

• Has fixed cycle of 3-5 p min. with amplitude of 5-15 bpm and above but not below the baseline.

• Should be viewed with suspicion as poor outcome has been seen (eg Feto-maternal haemorrhage)

Causes of Sinusoidal pattern• cord compression• hypovolemia• ascites• idiopathic(fetal thumb sucking)• Analgesics• Anaemia• Abruption

Saltatory pattern

• Seen During Fetal thumb sucking.• Could be associated with Hypoxia.

Fetal Blood SamplingWhy : -Persistent Abnormal CTG after reversible factors have been

corrected, -Persistent late decels and 2 abnormal other features e.g

baseline tachycardia or reduced B-B variability or just difficult to interpret the CTG

when: -Rom, -PP accessible and well applied Cervix dilatation >= 3 -Left lateral maternal position -Sterile environment and good light and equipment -Good analgesia

FBS-Cord PH

• Fetal blood sampling is sampling from Arteries.

• Normal value is 7.25-7.35• Less than 7.20 shows significant asphyxia• Values between 7.2 and 7.24 need further

evaluation• Low –normal PH should be repeated in 30 min• Less than 7.20 dicatates eminent delivery

FBS- Lactate

• FBS easier to interpret, difficult to perform

• Anaerobic metabolism can lead to metabolic acidosis

• Lactate levels more specific for degree of metabolic acidosis than Ph

• Lactate rises quicker and takes longer to resolve than Ph.

FBS Contraindications

FBS-Sampling errors

• Should be done Between decelerations• Excess pressure on PP reduces

perfusion• Should not be done on the caput

Points to remember• NST:Favorable: Increase15 bpm for 15 seconds within 20

min of beginning the test (before 32 wks of GA we consider 10bpm lasting 10 seconds)

• BPP:Pregnancy termination for: • reduced AF• Gestational age over 36 weeks• Score of 2

Repeating the BPP test for:• Score below 6 + less than 36 weeks gestation/ low Bishop/ L/S>2

Points to remember• Positive OCT: 50% or more of uterine

contractions accompany FHR decelerations• Variable deceleration: occurs >= three

times in a 20 min interval with FHR drop to 70 bpm

• Persistent deceleration: more than 30 bpm reduction in a 2-10 min interval

• Bradycardia: more than 30 bpm reduction of FHR in more than 10 min

+OCT: late decelerations following 50% or more of contractions

• 3 or more contractions• Lasting at least 40 seconds• In a 10-min period• By either spontaneous contractions or:

• 0.5 mU/min oxytocin • Doubled every 20 minutes

Hyperstimulation: frequency more than every 2 min or lasting longer than 90 seconds

Points to remember in BPP scoring:score two, otherwise zero

1-Tone: 1

2-Respiration: 1 of 30 sec

3-AF: 1pocket more than 2 cm

4-NST: 2 of 15 bpm of 15 sec in a 20 min strip

5-Movement: 3 in 30 min

Nonreassuring CTG patterns• Fetal tachycardia • Fetal bradycardia • Saltatory variability • Variable decelerations associated with a

nonreassuring pattern• Late decelerations with preserved beat-to-

beat variability

Ominous CTG patterns• Persistent late decelerations with loss of beat-

to-beat variability• Nonreassuring variable decelerations

associated with loss of beat-to-beat variability• Prolonged severe bradycardia• Sinusoidal pattern • Confirmed loss of beat-to-beat variability not

associated with fetal quiescence, medications or severe prematurity.

Diagnosis of ROM

• Conclusive: pooling of AF in the posterior fornix

• Nitrazine paper test: A PH above 6.5 is consistent with ROM(false positive with blood semen, vaginosis),(false negative with minimal fluid)

Dilation is ascertained

• By estimating the diameter of the cervical opening at the level of the internal os- which is the level where the examining fingers palpate the bag of water or fetal head.

Cephalic landmarks:

• Vertex: occipital fontanel• Bregma: anterior fontanel

Cardinal movements with more descent

• Engagement: greatest transverse diameter of the head (BPD) passes the inlet most often in LOT position.

• Flexion: suboccipitobregmatic diameter is substituted for the longer occipitofrontal diameter,

• Int rotation: happens at the level of the spine• Ext rotation(restitution): bisacromial diameter comes

to the AP diameter of pelvic outlet • Expulsion

Ritgen Maneuver

Maneuver to deliver the placenta

• The uterus is lifted cephalad with the abdominal hand

Abnormal labor criterianullipara multipara

Prolonged latent phase >20 h >14 hProtracted active phase dil <1.2 cm/h <1.5 cm/hProtracted descent <1cm/h <2 cm/hProlonged deceleration phase

>3h >1h

Secondary arrest of dil >2h >2hArrest of descent >1h >1hFailure of descent= No descent in decel. phase or 2nd stageMedian duration of the 2nd stage

50 minutes 20 minutes

Upper limit of the 2nd stage 2 hours 1 hour

Criteria to make an arrest diagnosis

• The latent phase has been completed with the cervix dilated 4 cm or more

• A uterine contraction pattern of 200 montevideo units or more in a 10 minute period has been present for 2 hours without cervical change

Montevideo units

If there are 5 contraction in a 10-minute window,

Peak contraction pressure of each contractionshould be subtracted from Baseline uterine

contraction Pressure.

Then the sum of these pressures generated is the number of montevideo units.

Labor management protocol in Parkland hospital

Women at term are admitted when cervical dil is 3-4 cm or more in the presence of uterine contractions .

Pelvic examinations should be performed every 2 hours.Amniotomy is performed two hours from admission.After 2-3 hours of hypotonic contractions and no cervical

progress high dose oxytocin stimulation is given.If delivery does not happen 8 hours or more from

admission, C/S is performed for dystocia.

Shoulder dystocia management1-Calling for help.2-an initial gentle traction 3-Emptying the bladder 4- episiotomy 5-Suprapubic pressure with downward traction to fetal head6- McRoberts maneuver (flexion of maternal thigh)7- Woodscrew maneuver8- attempting delivery of the posterior arm9-Intentional fracture of anterior clavicle or humerus , or

Zavanelli maneuver