Prospect for Vaginal Delivery of Growth-Restricted Fetuses With Abnormal Umbilical Artery Blood Flow

Abstract

Prompt operative delivery is commonly carried out when intrauterine growth restriction (IUGR) is suspected or there is absent or reversed end-diastolic blood flow velocity in the umbilical artery (UA). When resistance to UA blood flow is only slightly or moderately increased, however, there is no general agreement on when or how to deliver the fetus. The goal in this setting is to avoid exposing the fetus to hypoxia and distress when possible. A trial of vaginal delivery would be permissible only if there is a minimal risk of distress in labor. This prospective study evaluated planned vaginal delivery in 84 women with singleton term pregnancies if IUGR was suspected. UA Doppler velocimetry was carried out, as well as an oxytocin challenge test (OCT). The test was done at or after 36 weeks gestational age and, if it was negative, a trial of vaginal delivery was planned. UA Doppler velocimetry yielded normal findings in 51 cases but abnormal results in 33. In the latter cases, the pulsatility index was increased and forward-diastolic blood flow was maintained. These groups were similar in maternal age, parity, and the delay between the OCT and delivery. Mean gestational age at delivery was significant in the abnormal UA blood flow group. In addition, the OCT was positive more often (33% vs. 16%) in this group, and vaginal delivery was less frequent (40% vs. 63%). After labor had begun, 68% of women with abnormal UA blood flow and 76% of those with normal flow delivered vaginally. The vaginal delivery rate and transfer to the neonatal intensive-care unit did not differ appreciably in the 2 blood flow groups. Three infants with severely restricted growth had malformations, and 1 died as a result. One infant had meconium aspiration and pneumothorax but eventually was discharged home. Vaginal deliveries were significantly less frequent in the presence of abnormal UA Doppler velocimetry in this study, but when a trial of labor was ultimately done, the rates were similar in women with normal and those with abnormal blood flow patterns. There was no indication that any fetus was exposed to harmful hypoxia or distress. The OCT continues to be useful in some cases for assessing the status of growth-restricted fetuses and those with mild to moderate changes in UA blood flow.