Predictability of complications associated with prolongation of pregnancy.

The frequency of complications and fetal macrosomia occurring in 243 patients with excellent dates indicating that their pregnancy was prolonged beyond 40 weeks (280 days) was analyzed and compared with that from a control group of 250 normal patients whose pregnancy ended spontaneously between 38 and 40 weeks of gestation. Complications (intrapartum fetal distress, traumatic deliveries, meconium aspiration, postmaturity syndrome) were significantly more frequent in patients in the study group (25.1%) than in the controls (5.6%). Similarly, fetal macrosomia occurred significantly more often in the study patients (29.6%) than in the controls (10.4%). To study the efficacy of antepartum surveillance in predicting these abnormal events, the postterm patients were randomized between two plans of management: 126 were followed with weekly nonstress testing (NST), and 117 with NST plus weekly ultrasound evaluation of fetal size, amniotic fluid volume, and placental grade. Contraction stress testing (CST) was used if the NST was nonreactive. Electronic monitoring had positive and negative predictive values of 42.8 and 87.7%, respectively, whereas ultrasound-plus-electronic monitoring had values of 50 and 65.3%, respectively. These results indicate that the increased incidence of complications in pregnancy prolonged beyond 40 weeks cannot be adequately predicted with antepartum electronic monitoring and ultrasound evaluation of fetal size, placental grade, and amniotic fluid volume.