Does labor start too late?

Abstract

To determine the optimal time of delivery, in terms of lowest risk of peripartum complications, the relative incidences of the parameters. Abnormal cardiotocogram (CTG), operative vaginal delivery, Apgar < 7 at 1 and 5 min, artery cord blood pH < 7.20, blood loss > 500 ml, epidural anesthesia, and Cesarean section, were retrospectively analysed with regard to mode of labor onset (spontaneous, induced) and gestational age in all deliveries between gestational weeks (GW) 35 + 0/7 and 42 + 6/7 from 1986 through 1993 at Zurich University Hospital (n = 11,834) and additionally with regard to birth weight in the same population from 1987 through 1993 (n = 10,346). The distribution of most parameters was parabolic with nadirs at GW 37-38; the incidence of low Apgar scores and Cesarean sections, however, was lowest nearer term (GW 39-40). Mode of labor onset had little effect (< or = 1 week) on the time of lowest incidence. The birth weight associated with the fewest complications was 3000 g, with the optimal time of delivery being GW 37-38, assuming a birth weight normal for gestational age.