1. Postterm Pregnancy
UKSM-Wichita

2. I have no conflicts of interest to report.

3. Clinical considerations
Topics for Review
Definitions
Etiologic factors
Risk factors
Clinical considerations
Recommendations

4. Definitions Postterm Pregnancy (PTP): reached or
extended beyond 42 0/7 weeks
Late-Term Pregnancy (LTP): reached
between 41 0/7 weeks & 41 6/7 weeks
ACOG Practice Bulletin. #146, 08/2014.

5. Fetal Etiologic Factors
Male fetus
Anencephaly
-the physiologic reasons for these associations are unknown
Placental sulfatase deficiency
ACOG Practice Bulletin. # 146, 08/2014

6. Maternal Etiologic Factors
Nulliparity
Prior postterm pregnancy
-studies of twins suggested that a genetic predisposition may confer 23-30% of the risk of LTP & PTPs
Genetic predisposition
Obesity
ACOG Practice Bulletin. # 146, 08/2014

7. Increased Risks of LTP & PTP

8. Dysmaturity (Postmaturity) Syndrome
Infant appears malnourished with little
subcutaneous fat
Associated with increased risks of asphyxia,
meconium staining and aspiration
Occurs at term but markedly increased
after term
Boylan P. Curr Opin Obstet Gynecol 1990,2:31-5.

9. Increased Risks: Macrosomia
2x increased risk for macrosomia
Increased risks for OVD, C/S, &
shoulder dystocia
ACOG Practice Bulletin. #146:08/2014

10. Increased Risks: Macrosomia
GA Primip BW Multip BW
(gm, mean + SD) (gm, mean + SD)
-7000 infants assessed by sono between weeks
-concordance (+ or – 7 days) on basis of ultrasound & LMP; Excluded those not concordant and looked at them separately
-delivery at or after 39 weeks (273 days) from onset of normal LMP
-exclusion criteria were conditions known to disturb fetal growth (multiple pregnancies, maternal hypertension or diabetes, fetal Rh, erythroblastosis, NIH, and TORCH
-excluded patients as early ultrasound date > 14 days different than normal LMP, the mean BW was 3400 g, which is very close to that of term infants in the study
-when erroneous LMP are eliminated with the use of early ultrasound, mothers delivered large and not small babies
-severe IUGR defined as a BW at least 25% below the mean weight for GA; this definition corresponds to the 1.7^ for their hospital population
No difference between severe IUGR infants born
before or after term
McLean FH et al. AJOG 1991;164:

11. Increased Risks: Oligohydramnios Amniotic Fluid
Protects fetus from trauma & infection
Allows for fetal movement
Prevents compression of cord & placenta
-protects fetus by dampening effect and bacteriostatic properties
-movement and fosters the development of the fetal musculoskeletal system
-protects the fetus from vascular and nutritional compromise
-amniotic fluid is an important parameter in the assessment of fetal well-being

12. Oligo Has an Increased Risk For:
Fht problems
Cord compression
Meconium
Cord pH < 7
-associated in many high-risk conditions and is associated with poor perinatal outcomes -
Lower Apgars
ACOG Practice Bulletin. No. 146, 08/2014

13. Identifying Oligohydramnios
Amniotic fluid index
(AFI) < 5 cm
Largest Vertical Pocket
(LVP) < 2 x 1 cm
AFI increases interventions
without improvement in
pregnancy outcomes
-semiquantitative way to measure AF
-no clear consensus of the best method to assess amniotic fluid adequacy
-5 RCTs of 3226 women of low- and high-risk singleton pregnancy using the measurement of amniotic fluid volume as part of the antepartum assessment of fetal well-being that compared the AFI and the LVP or overall rate of C/S
=when AFI used, increased the diagnosis of oligo, more inductions of labor and C/S for fetal distress
-no evidence that one method is superior to the other in the prevention of poor peripartum outcomes, including admission to the NICU, pH < 7.1, presence of meconium, C/S, or an Apgar < 7 at 5 minutes
Nabhan AF et al. Cochrane Database of Systematic Reviews
2008, Issue 3.

14. Meconium Aspiration Syndrome (MAS)
Airway obstruction & chemical pneumonitis
Pulmonary hypertension & persistent fetal
circulation
Meconium inhibits surfactant function
-MAS important cause of respiratory distress in neonates, sometimes leading to respiratory failure and death
-pathophysiology of MAS caused by airway obstruction, chemical pneumonitis by aspirated meconium and pulmonary hypertension induced by in utero hypoxia
-meconium damages the alveolar epithelium and inhibits pulmonary surfactant function
MAS in post-term infants: 3.9/1000 vs
term infants 1.3/1000*
*Clausson B et al. Obstet Gynecol 1999;94:

15. Interventions to Avoid PTP

16. Inherent Errors of LMP Dating Variable duration of follicular phase,
Based on accurate recall of 1st day of LMP
-EDC calculated on assumption that pregnancy lasts 280 days from the first day of your LMP
-studies of PTP based on the LMP alone include many with erroneous dates
-follicular phase ends with ovulation
-as sperm can survive 4-5 days, can become pregnant 4 days before ovulation and up to 24 hours after
So unless you use an ovulation predictor kit, have IUI or IVF, the LMP is very unreliable
Variable duration of follicular phase,
that ranges from 7-21 days
Bennett KA et al. AJOG 2004;190,

17. RCT Comparing 1st & 2nd Trimester Dating
104 women in 1st trimester: 41.3% had
gestational age adjusted
92 women in 2nd trimester: 10.9% had
gestational age adjusted
5 women in 1st trimester and 12 women
in the 2nd trimester had labor induced for PTP
-Canadian study that Randomized 218 women to receive either 1st trimester ultrasound screening or 2nd trimester screening to establish the expected EDC
-in 1st trimester if GA differed from LMP by 5 days or more, GA from CRL used
-2nd trimester sono scheduled at 19 weeks GA by LMP and physical exam
-EDC changed if differed by > 10 days
-Conclusion: application of a program of 1st trimester ultrasound screening to a low-risk obstetric population results in a significant reduction in the rate of labor induction of PTP
P=.04, RR=.37, 95% CI 0.14, 0.96
Bennett KA. AJOG 2004;190:

18. Ultrasound for Fetal Assessment in Early Pregnancy
To assess if early ultrasound (<24 weeks)
influences management
Less likely to be induced for PTP:
RR 0.59, 95% CI 0.42, 0.83
PTP accounted for 13% of inductions
-8 studies reported rates of induction for PTP (25,516 patients; routine scan, control)
7 studies reported rates of missed multiples (295 patients, 153 routine scan, 142 control)
Less likely for missed multiples:
RR 0.07, 95% CI 0.03, 0.17
Whitworth M et al. Cochrane Database of Systematic
Reviews 2010, Issue 4.

19. Membrane Sweeping 13 studies b/w 37-40 wks. & 6 > 40 weeks;
2389 women
Reduction of 14% to use other methods to
induce labor: RR: 0.60; 95% CI:
Significantly more women had discomfort
& had bleeding, contractions
-Royals sweep LA
-Royals sweep Baltimore
-13 studies compared sweeping to no sweeping
-membrane sweeping involves the digital separation of the membranes from the lower uterine segment during a pelvic exam with a dilated cervix
-this intervention has the potential to initiate labor by increasing local production of prostaglandins and reduce pregnancy duration
-about 8 women need to have sweeping of membranes to avoid one formal induction of labor
-frequency of major side-effects was not increased
-contractions in 1st 24 hours after membrane sweeping that did not lead to labor
Questionable practice to perform in an
uneventful pregnancy before 38 weeks
Boulvain M et al. Cochrane Database of Systematic Review
2005,Issue 1.

20. Clinical Considerations: When to Deliver

21. Clinical Considerations: When to Deliver
22 RCTs : 9383 women
Grouped trials by induction at wks,
wks, 3. < 41 wks, wks,
5. > 41 wks compared to waiting
-as a pregnancy continues beyond term the risks of babies dying in utero or in the immediate newborn period increase. Whether a policy of labor induction at a predetermined GA can reduce this increased risk is the subject of this review
=selection criteria: RCTs conducted in women at or beyond term
=eligible trials were those comparing a policy of labor induction with a policy of awaiting spontaneous onset of labor
-expectant management group: 20 had various combinations of fetal monitoring; 2 had no interventions
-7 trials had no GA limit for induction and others IOL was from weeks
Gulmezoglu AM et al. Cochrane Database of Systematic
Reviews 2012, Issue 6.

22. Primary Outcome: Perinatal Death
Clinical Considerations: When to Deliver
Subgroup Risk Ratio (95% CI)
39-40 weeks (0.03, 3.09)
41 weeks (0.03, 3.17)
-number needed to treat with induction in order to prevent one perinatal death has 410 (95% CI )
>41 weeks (0.12, 0.99)
Gulmezohlu AM et al. Cochrane Database of Systematic
Reviews 2012, Issue 6.

23. Secondary Outcomes
Significant reduction in induction group at 41 wks in:
Meconium Aspiration Syndrome:
(RR 0.50, 95% CI 0.34, 0.73)
Birthweight > 4000 g:
(RR 0.73, 95% CI 0.64, 0.84)
-meconium aspiration syndrome: 8 trials with 2371 women; induction was at 41 weeks or > 41 weeks
-BW > 4000 g:6 trials with 5217 women; 41 or > weeks
-cesarean section 21 trials of 8749 women; induction at 41 weeks
Cesarean section:
(RR 0.89, 95% CI )
Gulmezogly AM et al. Cochrane Database of Systematic
Reviews 2012, Issue 6.

24. Other Secondary Outcomes
No significant difference between groups in:
NICU admission
Birth asphyxia
Apgar score < 5 minutes
Gulmezoglu AM et al, Cochrane Database of Systematic
Reviews 2012, Issue 6.

25. Antepartum Testing Begin at 41 0/7 weeks: from observational
data that stillbirth increases at this GA*
No difference b/w BPP & NST in perinatal
death (RR 1.35, 95% CI 0.6, 2.98) #
-no RCTs that demonstrate that AP testing decreases fetal M&M in LTP or PTP
-observational data indicates an increased risk of of stillbirth at or beyond 41 0/7 weeks, initiation of AP testing to begin at or beyond 41 0/7 weeks
-Cochrane review of 5 RCT and quasi-randomized trials of fetal surveillance in high-risk pregnancies that included PTP found no difference in perinatal death between the BPP and NST groups
Assessment for oligo is warranted*
#Cochrane Database of Systematic Reviews
2008, Issue 1.
*ACOG Practice Bulletin. #146, 08/2014.

26. Summary of Recommendations &
Conclusions
-studies of twins suggested that a genetic predisposition may confer 23-30% of the risk of late-term and postterm pregnancies

27. Level A Evidence & Recommendations
LTP & PTP: associated with an increased
perinatal M&M
Induce labor after 42 0/7 weeks & by
42 6/7 weeks
A: following conclusions are based on good and consistent scientific evidence
ACOG Practice Bulletin, Number 146, Aug. 2014

28. Level B Evidence & Recommendations
Membrane sweeping: decreased risk of
LTP & PTP
Induction between 41 0/7 weeks &
42 0/7 weeks can be considered
-Level B: following conclusions are based on limited or inconsistent scientific evidence
ACOG Practice Bulletin, Number 146, Aug. 2014

29. Level C Evidence & Recommendations
AP testing at or beyond 41 0/7 weeks
may be indicated
Level C are based primarily on consensus and expert opinion
ACOG Practice Bulletin, Number 146, Aug. 2014

30. Thank you for your attention!