Induction of labor in cases of late preterm isolated oligohydramnios: is it justified?

Objectives: To analyze in a retrospective cohort study the outcomes of pregnancies with isolated oligohydramnios at the late preterm period (34-36.6 weeks of gestation). Study design: This retrospective cohort study included three groups of women: (1) Women with isolated oligohydramnios whose pregnancy was managed conservatively (n = 33 births); (2) women with isolated oligohydramnios who were managed actively (i.e. induction of labor) (n = 111 births); and (3) a control group including women with normal amount of amniotic fluid who had a spontaneous late preterm delivery (n = 10,445 births). Maternal and fetal characteristics and obstetrics outcomes were collected from a computerized database of all deliveries at Soroka University Medical Center during the study period. Results: Our cohort included 10,589 births. The rate of inducing labor was higher in the oligohydramnios groups compared to the controls (p < .001). There was an increase in the rate of cesarean section (CS) in the conservative treatment group (p < .001), compared with the other groups. Conservative management was associated with higher rates of maternal infection (p = .026), chorioamnionitis (p = .01), and transitory tachypnea of the newborn (p = .02). After controlling for confounding factors, mal presentation (OR = 19.9), and a prior CS (OR = 2.4) were independently associated with an increased risk for CS, while induction of labor was associated with a reduced risk for CS (OR = 0.28). Conclusions: Women with late preterm isolated oligohydramnios had a higher rate of induction of labor than women with a normal amount of amniotic fluid. Induction of labor seems to be beneficial to both the neonate and the mother as seen by a lower rate of CS conducted in this group, as well as lower maternal and neonatal morbidity in comparison to the conservative group. Therefore, women with oligohydramnios at late preterm may benefit from induction of labor.