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)

-          Incidence is 5.5%

-          Risk factors include nulliparity, prior post term pregnancy, male fetus, obesity, anencephaly, genetic predisposition/family history

-          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)

-          TOLAC is okay. No increased risk of uterine rupture, however, failure rate is increased.


Avoiding Late-Term and Post-Term Pregnancy

-          Accurate dating with “firm clinical criteria” or early ultrasound

-          Membrane sweeping

Antepartum Fetal Surveillance in Late-Term and Post-Term Pregnancy

-          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

-          Insufficient data re: type (CST, NST, M-BPP, BPP) and frequency of surveillance…twice weekly may be better, but no conclusive evidence.

-          “Ultrasonographic assessment of amniotic fluid volume is warranted”…MPV <2cm -> delivery


Induction of Labor

-          RCTs: increased C/S in expectant management group

-          Cochrane Review: increased C/S, perinatal death, meconium aspiration in expectant group

o   Number needed to treat…410 inductions to prevent one perinatal death

-          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.”