Post-term Pregnancy

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Post-term Pregnancy

• Khalid A. Yarouf

. www.4MedStudents.com
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Gestational age at pregnancy termination

• Abortion lt 24 weeks from LMP.
• Preterm delivery 24-37 weeks.
• Term 38-42 weeks.
• Post-term gt 42 weeks.
• 10 of pregnancies.
• Occur more frequently in primigravida, who are
  younger or older than average childbearing age,
  and in grandmultiparas (women who have had 6
  successful pregnancies).

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What is the best estimate for gestational age?

• Hx
• LMP tends to be reliable if LMP was definite,
  cycle was normal, and pregnancy was planned.
• Quickening (maternal perception of fetal
  movement) occurs at about 16-20 weeks.
• P/E
• Size of uterus at early examination in 1st
  trimester should e consistent with dates.

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Cont

• Apply Naegeles rule
• Add 7 days to the date of the first day of the
  LMP ? count back 3 months.
• e.g. LMP was March 7, 2001 ? EDD would be January
  14, 2002.
• Note that the length of gestation increases
  approx. 1 day for each day the menstrual cycle is
  gt 28 days.

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Cont

• Obtain US (confirmatory)
• Fetal heart can be heard starting at 11 weeks.
• Crown-rump length (CRL)
• Most accurate in 1st trimester to within 5
  days.
• At 12 weeks, fetus begins to curve this
  measurement becomes lt accurate.
• Biparietal diameter (BPD) from 12-18 weeks is
  most accurate to 7 days.

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What are the causes of post-term pregnancy?

• Potential causative factors
• Deficiency of ACTH in fetus placental sulfatase
  deficiency.
• Exact mechanism of spontaneous onset of labor in
  unclear, but fetus, placenta mother are all
  involved. The longest pregnancy on record is 1
  year 24 days, ending in a liveborn anencephalic
  infant. CNS abnormalities, e.g. anencephaly, are
  a/w prolonged pregnancy.

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What are the complications of prolonged pregnancy?

• Incidence of fetal mortality for all groups is as
  follows
• 40-41 weeks gestation 1.1
• 43 weeks gestation 2.2
• 44 weeks gestation 6.6
• Macrosomia
• Commonest outcome (75).
• Occurs if placental function is maintained.
• Cx of large uterus
• Arrest of labor Cesarean delivery Traumatic
  vaginal delivery.

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Cont

• Dysmaturity syndrome
• Normally, theres little growth of fetus
  post-term.
• This syndrome is observed in 30 of post-term
  infants in 3 of term infants.
• CFx
• Loss of subcutaneous fat.
• Dry, wrinkles, cracked skin.
• Long nails.
• Unusual degree of alertness.
• Cx Fetal hypoxia Meconium aspiration syndrome.

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Cont

• Placental aging / senescence ? Critically ?
  nutritional O2 supply ? Fetal compromise 2 to
  placental insufficiency (major concern in
  post-term pregnancy).
• Oligohydramnios
• Morbidity increased with HTN/ preeclampsia, DM,
  abruption, IUGR, multiple gestation.

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How can you assess the post-term fetus
antenatally?

• FHR testing
• NST (non-stress test)
• Non-invasive test of fetal activity that
  correlates with fetal well-being.
• Fetal heart rate accelerations are observed
  during fetal movement.
• External monitor is used to record FHR mother
  precipitates by indicating fetal movement.
• NST can be reactive or non-reactive.
• Contraction Stress test not used anymore.

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Cont

• Biophysical profile (BPP)
• Composite of tests designed to identify a
  compromised fetus during antepartum period.

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Biophysical Profile (BPP)
Parameter Normal (2 points) Abnormal (0 point)
Amniotic Fluid Volume (AFV) Fluid pockets of 2 cm in 2 axes. Oligohydramnios
NST Reactive. Non-reactive
Breathing At least 1 episode of breathing lasting at least 30 sec. No breathing
Limb movement 3 discrete movements. 2
Fetal tone At least 1 episode of limb extension followed by flexion. No movement
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Cont
Score Interpretation Mx
8-10 Normal Repeat BPP as clinically indicated
6 Suspect chronic hypoxia Repeat BPP in 4-6 hours
0-4 Strongly suspect chronic asphyxia Deliver fetus if mature
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How can you manage suspected post-dates pregnancy?

1. Determine gestational age dating.
2. Establish how favorable cervix is (dilated,
   effaced, soft).
3. Assess fetal well-being e.g. with NSTs
   amniotic fluid indices (AFIs). If fetal
   jeopardy is evident, immediate delivery is
   appropriate.

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Cont

• Use the following triage method
• Dates are certain cervix is favorable. Neither
  the mother nor the fetus benefits from waiting ?
  induce labor promptly with IV oxytocin rupture
  of membranes.
• Dates are certain but cervix is unfavorable.
  Risk of failed induction is high. If fetal
  macrosomia is suspected, induce labor with PGE2.
  Alternatively, if the estimated fetal weight
  (EFW) is normal, manage expectantly with
  twice-weekly NSTs AFIs.
• Dates are unsure. Because its not known if the
  patient is post-dates, delivery is not indicated.
  Manage expectantly with twice-weekly NSTs AFIs
  awaiting spontaneous labor.

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Cont

• Intrapartum Mx of Cx
• Meconium staining
• Prior to delivery ? Amnio-infusions
• infusion of NS thru intrauterine catheter.
• to dilute meconium.
• After delivery of fetal head ? suctioning
  meconium from nose pharynx to prevent
  aspiration.
• After delivery of entire fetus, but before the
  first neonatal breath ? aspirate neonatal
  tracheal meconium using laryngoscope.

17
Cont

• When macrosomia is suspected, US should be
  performed to estimate fetal weight. Clinician
  should always be prepared to deal with a
  potential shoulder dystocia.
• Intrapartum asphyxia Careful monitoring should
  be instituted when this is suspected.