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Management of Postterm Pregnancy


LMP reports prolonged gestation 2.8 days longer on average than ultrasound scanning, ... Accurate dating by early sono---not current standard of prenatal care in the US. – PowerPoint PPT presentation

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Title: Management of Postterm Pregnancy

Management of Postterm Pregnancy
  • Leslie Ablard, MD
  • OB/GYN
  • Mowery Womens Clinic
  • Salina, KS

Postterm 42 weeks
Definition ACOG 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
  • 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

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

Assessment of gestational age
  • Accurate dating is important for minimizing the
    false diagnosis of postterm 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
  • When did you first find out you were pregnant?

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).

Accuracy of LMP
  • Comparison of pregnancy dating by last menstrual
    period, ultrasound scanning, and their
    combination. Am J Obstet Gynecol. 2002
  • 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

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

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

Risks to the fetus
  • Approx 20 of postterm fetuses have dysmaturity
  • 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

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

Are there interventions that decrease postterm
  • Accurate dating by early sono---not current
    standard of prenatal care in the US
  • Membrane sweeping studies are conflicting

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

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)

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
  • 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

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

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
  • 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

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

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

  • 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

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

  • 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)

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

Friedman curve
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

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
  • Many c-sections performed when not even in active
  • Dont be afraid of serial inductions
  • Use all your armamentarium- prostaglandins, foley
    bulb, pitocin, AROM, FSE, IUPC, operative

  • 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
  • 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

Postterm Pregnancy is like Popcorn
Thank you