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Late/Post
Term Pregnancy PB146
Late term = 41 0/7 – 41 6/7 (OR of stillbirth is 1.5 at 41 weeks)Post
term = 42 0/7 and beyond (OR of stillbirth is 1.8 at 42 weeks and 2.9 at
43 weeks)
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Incidence is
5.5%
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Risk factors
include nulliparity, prior post term pregnancy, male fetus, obesity,
anencephaly, genetic predisposition/family history
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Higher risk of
neonatal convulsions, meconium aspiration, 5-minute Apgar <4, NICU
admit, oligohydramnios, macrosomia, shoulder dystocia, perineal
laceration,
operative delivery, maternal infection, postpartum
hemorrhage, cesarean, postmaturity syndrome in 10-20% (decreased SQ
fat, no vernix or lanugo)
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TOLAC is okay.
No increased risk of uterine rupture, however, failure rate is
increased.
Avoiding Late-Term and Post-Term Pregnancy
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Accurate dating
with “firm clinical criteria” or early ultrasound
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Membrane
sweeping
Antepartum Fetal Surveillance in Late-Term and Post-Term Pregnancy
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No studies have
confirmed benefit in terms of perinatal morbidity/mortality, but
given increased risk of stillbirth, it seems reasonable to start
surveillance “at or beyond” 41 0/7 weeks
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Insufficient
data re: type (CST, NST, M-BPP, BPP) and frequency of
surveillance…twice weekly may be better, but no conclusive evidence.
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“Ultrasonographic assessment of amniotic fluid volume is
warranted”…MPV <2cm -> delivery
Induction of Labor
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RCTs: increased
C/S in expectant management group
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Cochrane Review:
increased C/S, perinatal death, meconium aspiration in expectant
group
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Number needed to
treat…410 inductions to prevent one perinatal death
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ACOG Summary:
“IOL between 41 0/7 weeks and 42 0/7 weeks can be considered. IOL
after 42 0/7 weeks and by 42 6/7 weeks of gestation is recommended.”
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