Prolonged Pregnancy

1. Prolonged Pregnancy Ashley C. Lindell, MD Swedish Family Medicine

2. Questions • What is postterm pregnancy? • Why does it matter? • How should it be managed?

3. A case... • 26 year old G1 (?2) P1 presents with amenorrhea and nausea. The first day of her LMP was about 2 months ago, she doesn’t remember the exact date. It was a normal period. She reports “pretty regular” menses, about once a month. Her urine pregnancy test is positive. • Question #1: What is her EDC?

4. Definitions • Postterm/prolonged pregnancy = to or beyond 42 weeks post first day of LMP • perinatal mortality data derived from accurately dated pregnancies suggest increased risk from 41 weeks onward

5. Dating (all that stuff in the box on the blue-border form) • Clinical -certain LMP = +/- 14 days -fundal height, quickening, FHT’s = +/- 15-17 days problems with LMP dating: 1. Approximately 1/3 of women don’t remember the first day of their LMP 2. Variable length of menstrual cycle, particularly of the follicular phase -> overestimation of GA

6. Dating, part 2 • Ultrasound - early US (< 24 weeks) decreases the number of pregnancies diagnosed as postterm Accurate dates = accurate diagnosis - most common cause of “postterm” is inaccurate dating - may be based on a definite LMP in women with regular, normal menses + confirmatory uterine sizing; any uncertainty in clinical dating parameters -> US - some recommend universal early US for dating

7. Back to your OB • Since she can’t remember her exact LMP, you decide to get an early US for dates. You draw prenatal labs, prescribe PNVs, and do an H&P. • Her first child was induced at 42 weeks. She tells you she had a long labor, that her doctor put a monitor on the baby’s scalp because the heart rate kept going down, and that the baby’s shoulder got stuck. • You wonder: A. Is she at increased risk of going postdates again? B. What should I be concerned about if she does ? C. Should I transfer her to perinatal?

8. Postterm-who cares? • You should It’s common: approximately 10% of US pregnancies -> you’ll be managing it Risk is increased significantly (2-3 X) in women with a previous postterm delivery; risk is increased slightly in primips and women who are the product of a postterm pregnancy Perinatal morbidity and mortality is increased in prolonged pregnancies

9. Physiology Review • uteroplacental insufficiency increased risk of oligo, abnormal FHT’s, meconium/MAS, low Apgars, hypoglycemia, seizures, respiratory insufficiency • fetal growth linear function of GA 37- 42 weeks; bigger babies = increased risk of cephalopelvic disproportion/macrosomia -> dysfunctional labor, shoulder dystocia, maternal trauma, hemorrhage

10. M&M • Mortality perinatal mortality (fetal + early neonatal): 40 weeks = 2-3/1,000; 42 weeks = 4-7/1,000 (Feldman, Bakketeig) fetal loss/1,000 live births, OR vs. term: 41 weeks = 1.5, 42 weeks = 1.8, 43 weeks = 2.9 (Divon) fetal loss/1,000 ongoing pregnancies: 37 weeks = 0.7, 40 weeks =2.4, 43 weeks =5.8 (Hilder)

11. M&M, part 2 • Morbidity RR at >/= 42 weeks vs. term: fetal distress = 1.7, shoulder dystocia = 1.3, dysfunctional labor = 1.3, ob trauma = 1.25, hemorrhage = 1.1 (Campbell) other studies(Clausson, Alexander, Tunon): increased labor complications - prolonged/dystotic labor, forceps, c-sections increased perinatal morbidity - convulsions, MAS, low Apgars, NICU admissions

12. Back to your patient • Her pregnancy proceeds normally • At 37 weeks you A. Put her name to the moms and babes signout B. Start wondering how you should manage her pregnancy if she goes past her EDC. C. Review your ALSO material on shoulder dystocia. D. All of the above.

13. Management: To induce or not to induce? And when? • Factors to consider gestational age (aren’t you happy you got that <24 week US?) cervix-favorable vs. unfavorable results of antepartum fetal monitoring patient preference overall balance of risks of expectant management vs. risks of induction

14. Antenatal testing • goal = prevent fetal death by detecting early signs of placental dysfunction/ fetal compromise • abnormal test results (oligo, abnormal fetal heart rate tracing)= delivery • Options: BPP, NST + AFI, CST -all have low false negative rates; < 0.1% (fetal demise within 1 week of normal test result) (ACOG Practice Bulletin) -all have high false positive rates (abnormal test, no fetal compromise intrapartum); 40% for BPP, 60% for NST + AFI, 65% for CST (Miller, ACOG Practice Bulletin)

15. Antenatal Testing, part 2 • What’s the data? Efficacy of antenatal testing in improving outcomes has not been validated (ACOG, UTD). No specific protocol of antenatal testing has been shown to be superior. (ACOG, UTD) • So what am I supposed to do? -ACOG: begin testing by 42 weeks, insufficient evidence testing at 40-42 weeks improves outcomes, no recommendation on protocol -community standard of care/expert opinion: 2X weekly testing including AFI beginning in 41st week

16. IOL vs monitoring: the data • largest trial routine postterm IOL (41 weeks) vs monitoring: perinatal M&M rates same, lower c-section rate with IOL (Hannah) • Multiple other trials-> mixed results • Cochranemeta-analysis (1999) 19 trials routine IOL at 41+ weeks vs monitoring: perinatal mortality rates lower with IOL, c-section rates same • systematic review (2003) of 16 RCTs IOL at 41+ weeks vs expectant management: perinatal M&M not significantly different; c-section rates lower with IOL

17. IOL vs Monitoring: Recommendations • ACOG Practice Bulletin (1997!): Favorable cervix: Unknown whether IOL or expectant management preferable; labor is usually induced. Unfavorable cervix: Good evidence that either option results in good outcomes. • Up to Date: Recommend routine IOL at 41 weeks.Risks IOL lower with cervical ripening agents. Risks expectant management low, but risk of fetal death exists. • Cochrane (2000): Routine IOL at 41 weeks appears to reduce perinatal mortality

18. Your patient... • You add her to the signout and review shoulder dystocia. • You discuss the options and decide on IOL at 41 weeks. • In clinic at 40 1/2 weeks you do a cervical exam and note her Bishop score to be 3. • You wonder: “What should I do about that cervix?”

19. Cervical ripening /IOL- nonpharmacologic mechanisms: mechanical dilation, prostaglandin release risks: infection, bleeding, ROM, discomfort • Mechanical: foley, laminaria effective for ripening, similar failure rates (evidence level A) • Surgical: stripping of membranes -Cochrane: SOM alone does not produce clinically significant benefit; as an adjunct it is associated with decreased mean pit dose, increased rate of normal vaginal deliveries -meta-analysis: SOM at term shortens duration of pregnancy by a mean of 4 days; NNT to prevent 1 postterm pregnancy = 25 (Gabbe)

20. Pharmacologic Methods • Prostaglandins increase likelihood of vaginal delivery within 24 hrs (Cochrane) risks: uterine hyperstim, FHR changes 1. PGE2 dinoprostone-gel (prepidil) -insert (cervadil) 2. PGE1 misoprostol: decreased c-section rate, reduced need for pit vs placebo (evidence level A); CI with previous c-section

21. What about sex? • Herbs: traditional use, case reports (AFP, 5/03) • Castor oil, hot baths, enemas, sex -1 study on castor oil -> no difference in outcomes (AFP 5/03) -sex: 1 study -> minimally useful data (AFP 5/03); a nice theory, though- nipple + lower uterine segment stimulation->prostaglandin release, orgasm->uterine contractions • nipple stimulation: 2 studies->difference in intervention group, study design poor (AFP 5/03) 1 study: 3 hrs/day starting at 39 weeks-> decreased incidence of reaching 42 weeks without spontaneous onset of labor (Clinics FP 2001)

22. L&D • You get her on the induction schedule at 41 weeks • After 2 rounds of misoprostol, her Bishop score is 10 (4/60%/soft/anterior/-1) and you start pit • She progresses well on pit, is complete 4 hours later, and pushes for 1 1/2 hours to deliver a 7 lb 2 oz girl with good Apgars (and no shoulder dystocia!) • Was it the week earlier that made the difference? Was it being a multip? Was it luck? Do you care?

23. Summary • Accurate dating is important; have a low threshold for getting an early (<24 week) US to establish dates. • Postterm pregnancy is associated with increased maternal and fetal risks. • Either routine IOL at 41+ weeks or 2X/week monitoring starting in the 41st week with IOL for abnormal test results is reasonable; literature reviews suggest slightly improved outcomes with routine IOL. • With a Bishop score <6, cervical ripening is recommended before IOL. Mechanical dilators, PGE1 and PGE2 are all effective. Stripping of membranes may be useful in decreasing the number of pregnancies reaching 41 or 42 weeks and as an adjuct to pit.