Management of postterm pregnancy involves balancing risks to the fetus and mother. Postterm is defined as past 42 weeks gestation. Accurately dating the pregnancy is important to avoid false diagnosis. Risks to the fetus include stillbirth, meconium aspiration, and macrosomia. Risks to the mother include dystocia and infection. Studies show inducing labor at 41 weeks reduces stillbirths without increasing C-sections. Methods of antenatal testing after 41 weeks are debated, though monitoring is recommended. While an unfavorable cervix was viewed as a risk factor for C-section, recent evidence suggests underlying issues may be more important. Further research is needed to determine the optimal time for induction to minimize risks

1. Management of
Postterm
Pregnancy
Dr Ufaque Batool
House Officer
1

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. Obstet Gynecol.
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 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

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 Cervix Obstetrics & 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