Non-reassuring fetal status in the prolonged pregnancy: the impact of fetal weight

Objective To evaluate the incidence of abnormal fetal findings and Cesarean delivery for non-reassuring fetal status as a function of birth weight in the uncomplicated prolonged pregnancy. Methods Seven hundred and ninety-two patients at or beyond 41 weeks' gestat ion were managed expectantly. Population-specific birth-weight percentiles were calculated. Fetuses were retrospectively categorized as small (birth w eight < 10th percentile), average (10th percentile less than or equal to bi rth weight less than or equal to 90th percentile) or large (birth weight > 90th percentile). The incidences of abnormal antepartum fetal testing resul ts (i.e. oligohydramnios and/or abnormal nonstress testing) and Cesarean de livery for intrapartum non-reassuring fetal status were calculated for thes e three birth-weight categories. Results There was a significant inverse relationship between the incidence of abnormal fetal testing and birth-weight category (36%, 14% and 9% for sm all, average and large fetuses, respectively, P < 0.001). Small fetuses wer e more likely to require a Cesarean delivery for non-reassuring fetal statu s during labor than were all other fetuses (12.3% vs. 5.3%, P = 0.024). Conclusions The frequency of oligohydramnios and abnormal non-stress testin g is inversely related to birth weight in the expectantly managed prolonged pregnancy. In addition, small fetuses born at or beyond 41 weeks' gestatio n have an increased rate of Cesarean delivery for intrapartum non-reassurin g fetal status.