Management of Postterm Pregnancy

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Management of Postterm Pregnancy

• Leslie Ablard, MD
• OB/GYN
• Mowery Womens Clinic
• Salina, KS

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Postterm 42 weeks
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DefinitionACOG Bulletin 55, Sept 2004

• Postterm pregnancy refers to pregnancies that
  extend beyond 42 weeks gestation (294 days, or
  estimated date of deliver (EDD) 14 days)
• Accurate pregnancy dating is critical to the
  diagnosis
• The term postdates is poorly defined and should
  be avoided
• Although some cases are a result of the inability
  to accurate define the EDD, many cases result
  from a true prolongation of gestation
• Reported frequency of postterm pregnancy is 7

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Etiologic factors

• Most frequent cause of prolonged gestation
• A. Placental Sulfatase deficiency
• B. Error in Dating
• C. Fetal Anencephaly
• Other Associations
• Male Sex
• Genetic Predisposition
• Primiparity
• h/o prior postterm pregnancy
• When postterm pregnancy truly exists, the most
  common cause is
• Unknown

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Assessment of gestational age

• Accurate dating is important for minimizing the
  false diagnosis of postterm pregnancy
• MOST RELIABLY AND ACCURATELY DETERMINED EARLY IN
  PREGNANCY
• Questions at new ob visit
• When was the first date of your last period?
• Do you have regular cycles?
• Approx how many days between cycles?
• Are you sure about the given date?
• Where you on any birth control when you got
  pregnant?
• When did you first find out you were pregnant?

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Accuracy of LMP

• There are many inaccuracies in even the surest
  of LMPs
• Recall
• Delayed Ovulation
• Irregular cycles
• Predicting delivery date by ultrasound and last
  menstrual period in early gestation. Obstet
  Gynecol. 2001 Feb97(2)189-94.
• The last menstrual period (LMP) was considered
  certain in 13,541
• When ultrasound was used instead of certain LMP,
  the number of postterm pregnancies decreased from
  10.3 to 2.7 (P lt.001).

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Accuracy of LMP

• Comparison of pregnancy dating by last menstrual
  period, ultrasound scanning, and their
  combination. Am J Obstet Gynecol. 2002
  Dec187(6)1660-6
• 3655 women with sure LMP
• LMP reports prolonged gestation 2.8 days longer
  on average than ultrasound scanning, yielded
  substantially more postterm births (12.1 vs
  3.4), and predict delivery among term births
  less accurately

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Ultrasound dating?

• When sure LMP and US vary greater than 8
• Approx 7 days up to 20 weeks
• 14 days between 20-30 weeks
• 21 days beyond 30 weeks

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Risks to the fetus

• Risk of perinatal mortality (stillbirth and early
  neonatal deaths) TWICE that of term.
• 4-7 deaths vs 2-3 deaths per 1,000 deliveries
• Increases SIX fold and higher at 43 weeks
• Uteroplacental insufficiency
• Meconium aspiration
• Intrauterine infection
• Postterm pregnancy is an independent risk factor
  for low umbilical artery pH at delivery and low 5
  min APGAR scors
• Higher incidence of fetal macrosomia, although no
  evidence supports inducing labor as a
  preventative measure in such cases
• Prolonged labor, CPD, Shoulder Dystocia

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Risks to the fetus

• Approx 20 of postterm fetuses have dysmaturity
  syndrome
• Infants with characteristics resembling chronic
  IUGR from uteroplacental insufficiency
• Oligo, meconium aspiration, hypogycemia,
  seizures, respiratory insufficency,
  non-reassuring fetal testing
• Long term sequelae not clear
• One large prospective follow up study of children
  1-2 yrs, general intelligence, physical
  milestones, and frequency of intercurrent
  illnesses were not significantly different
  between normal infants born at term and those
  born postterm
• Fetuses born postterm are at increased risk of
  death within the first year- most have no known
  cause

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Risks to the pregnant woman

• Increased labor dystocia- 9-12 vs 2-7
• Increased risk in severe perineal injury related
  to macrosomia- 3.3 vs 2.6
• Doubled rate of c-section----endometritis,
  hemorrhage, thromboembolic events
• ANXIETY

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Are there interventions that decrease postterm
pregnancy?

• Accurate dating by early sono---not current
  standard of prenatal care in the US
• Membrane sweeping studies are conflicting

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When should antenatal testing begin?

• No studies to state when the best time to start,
  frequency, or type of testing to use (no one with
  include an unmonitored control group)
• No data that testing adversely affects patients
  experiencing postterm pregnancy
• So, DO IT

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Perinatal Mortality

• Figure 1. (A) The rates of stillbirth (-?-) and
  infant mortality (-) for each week of gestation
  from 28 to 43 weeks expressed per 1000 live
  births. (B) The rates of stillbirth (dark gray)
  and infant mortality (light gray) in the same
  population of 171,527 singleton births expressed
  as a function of 1000 ongoing (undelivered)
  pregnancies.

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What form of Testing?

• Options include NST, BPP, modified BPP (NST with
  AFI), Contraction Stress Test
• No single method superior
• Evaluation of AFI important
• Definition of oligo in the postterm not been
  established
• No vertical pocked more than 2-3 cm
• AFI less than 5
• My choice- starting at 41 weeks- twice weekly
  monitoring including NST with modified BPP (NST
  AFI)

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Induce or wait

• Management of low-risk postterm pregnancy is
  controversial
• Factors to include- gestational age, results of
  antenatal testing, cervix, maternal preference
• Many studies exclude those with favorable cervices

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Unfavorable cervix

• Small advantage using cervical ripening agents
• Several large multicenter randomized studies of
  management after 40 week report favorable
  outcomes with routine inductions starting at 41
  weeks
• Largest study found that routine induction at 41
  weeks, found elective induction resulted in lower
  c-section rates primarily related to fewer c/s
  for non-reassuirng fetal heart rate tracings
• Patient satisfaction was also higher
• Meta-analysis of 19 trials found that routine
  induction after 41 weeks was associated with a
  lower rate of perinatal mortality and no increase
  in c/s rate and no effect on operative vag
  delivery, use of analgesia, or FHRA

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Induce at 41 weeks?

• Large amounts of evidence suggest that routine
  induction at 41 weeks gestation has fetal benefit
  without incurring the additional maternal risks
  of a higher rate of c-section.
• This conclusion has not been universally accepted
• Smaller studies report mixed results
• Two studies reported an increase in c/s rate
  among certain subgroups of patients high risk

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Prostaglandins for induction

• Valuable tool
• Several placebo controlled trails have reported
  significant changes in Bishop scores, duration of
  labor, lower maximum doses of oxytocin, and
  reduced incidence of c/s.
• No standardized doses have been established
• Higher doses (especially PGE1) have been
  associated with tachysystole and hyperstimulation
  resulting in non-reassuring fetal status
• Lower doses are preferable with PG is used and
  FHR monitoring should be done routinely before
  and after placement

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VBAC

• Do not use prostaglandins
• Foley bulb pitocin
• Limited evidence on the efficacy or safety of
  VBAC after 42 weeks- no firm recommendations can
  be made

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Induction of labor

• 41 weeks?
• Consistently shown to have no increased
  morbidity/mortality even with nulliparous
  patients and unfavorable cervices
• 39 weeks?
• Multiparous patients appear to have no increase
  risk of c/s, morbidity, mortality
• Do have increased use of resources
• Conflicting data on nulliparous
• Recent study found no increase risk of c/s with
  unfavorable cervix after eliminating medical
  inductions (preeclampsia, diabetes, etc)
• Elective Induction Compared With Expectant
  Management in Nulliparous Women With an
  Unfavorable Cervix Obstetrics Gynecology.
  117(3)583-587, March 2011.
• May be a baseline risk for c/s un-related to
  gestational age or cervix

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• 2447 women underwent c/s from 30 hospitals in LA
  and Iowa
• 25 c/s performed for failure to progress at 3
  cm or less
• 40 of prolonged 2nd stage did not meet ACOG
  criteria (45 nulliparous)

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Indications for c/s

• -32,443 patients undergoing c/s 2003-2009
• - Obstet Gynecol 2011

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Friedman curve
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Zhangs new labor curve- sept 2010

• 26,838 women in non-augmented, active labor
• Multiparous do not enter active labor until 5 cm
• Nulliparous do not ener active labor until 6 cm
• Labor progresses more slowly than previously
  described

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Give em a chance!!

• Friedman was wrong ( or wrong for today)
• Labor curve of modern times is slower with the
  active phase in primips not occurring until 6cm
  dilated!
• Many c-sections performed when not even in active
  labor
• Dont be afraid of serial inductions
• Use all your armamentarium- prostaglandins, foley
  bulb, pitocin, AROM, FSE, IUPC, operative
  delivery

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summary

• Postterm pregnancy may in itself be high risk
• Establish a EDD early and as precisely as
  possible- early sono?
• Consider antenatal testing at 41 weeks vs
  induction
• An unfavorable cervix may not be as much of a
  risk factor for c-section as underlying issues-
  macrosomia, fetal intolerance to labor, etc.
• Where is the nadir for fetal well-being and
  maternal outcomes? 39 weeks? 41 weeks?
• Patience is important for todays labor curve

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Postterm Pregnancy is like Popcorn
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Thank you