Management of Postterm Pregnancy

1. Management of Postterm Pregnancy Leslie Ablard, MD OB/GYN Mowery Women’s Clinic Salina, KS

2. Postterm = 42 weeks

3. 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 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%

4. 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

5. 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?

6. 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. ObstetGynecol.2001 Feb;97(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 <.001).

7. Accuracy of LMP • Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol. 2002 Dec;187(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

8. 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

9. 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

10. Risks to the fetus • Approx 20% of postterm fetuses have dysmaturity syndrome • Infants with characteristics resembling chronic IUGR from uteroplacentalinsufficiency • 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

11. 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

12. 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

13. 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

14. 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.

15. 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)

16. 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

17. 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

18. 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”

19. 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

20. 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

21. 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 CervixObstetrics & Gynecology. 117(3):583-587, March 2011. • May be a baseline risk for c/s un-related to gestational age or cervix

22. 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)

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

24. Friedman curve

25. Zhang’s 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

26. 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 • Don’t be afraid of serial inductions • Use all your armamentarium- prostaglandins, foley bulb, pitocin, AROM, FSE, IUPC, operative delivery

27. 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 today’s labor curve

28. Postterm Pregnancy is like Popcorn

29. Thank you