Amniotic fluid index in the uncomplicated term pregnancy - Prediction of outcome

OBJECTIVE: To establish whether an association between oligohydramnios and pregnancy outcome is present in the uncomplicated term pregnancy. STUDY DESIGN: Pregnancies with a singleton fetus in cephalic presentation a t term (greater than or equal to 37 weeks), a reactive nonstress test and a n antepartum amniotic fluid index performed within four days of delivery be tween January 1994 and September 1998 were identified. Excluded were those with any maternal or fetal complication or unavailable outcome information. The primary outcome measure was rate of operative vaginal or abdominal del ivery for a nonreassuring fetal heart rate tracing. Statistical analysis in cluded Fisher's exact test and one-way analysis of variance, with a two-tai led P<.05 considered significant. RESULTS: Two hundred thirty-two women met the inclusion criteria; of them, 44 (19%) had an amniotic fluid index <less than or equal to>5 cm. There was no difference in the operative delivery rate for a nonreassuring fetal hea rt tracing between those with a normal amniotic fluid index >5 cm vs. less than or equal to5 cm (39 [21%] vs. 5 [11%], P>.05). In addition, there were no differences between the two groups in rates of neonatal intensive care unit admissions or five-minute Apgar scores <7. Patients with a normal amni otic fluid index had a significantly lower labor induction rate (96 [51%] v s. 42 [98%], P<.001) and higher rate of meconium-stained amniotic fluid (65 [35%] vs. 7 [16%], P=.01) than those with a low amniotic fluid index. CONCLUSION: In the uncomplicated pregnancy at term, an amniotic fluid index less than or equal to5 cm increases the incidence of labor induction but d oes not appear to affect the rate of operative delivery for abnormal fetal heart rate tracings.