A randomized study to assess the efficacy of the amniotic fluid index as a fetal admission test

Abstract

Objective: To determine whether there is a difference in the incidence of abdominal delivery for presumed fetal distress in women who have an intrapartum fluid index assessment and those who do not.

Methods: Over a 7-month period, parturients at 26-42 weeks' gestation and in early labor were randomized to the study (measured amniotic fluid index [AFI] on admission) or a control group (no sonographic assessment of amniotic fluid [AF] volume). The labor and delivery staff were aware of the AFI results of the study subjects. All patients had continuous electronic fetal monitoring, and none had an abnormal tracing on admission. Student t test or chi 2 was used for statistical analysis. P < .05 was considered significant.

Results: The study (N = 447) and control groups (N = 436) had similar maternal demographics as well as medical and obstetric complications. In the study group, the incidence of abdominal delivery for fetal distress (29 of 447) was significantly higher than among controls (14 of 436) (P = .02; relative risk 1.3, 95% confidence interval 1.1-1.7). Among parturients who had abdominal delivery for fetal distress, the decision-to-incision times (mean +/- standard deviation) were similar for parturients who had undergone assessment of AFI and those who had not (38.5 +/- 14.7 versus 32.5 +/- 14.7 minutes, respectively; P = .47). Mean birth weight, incidence of low birth weight, macrosomia, Apgar scores less than 7, and the number of admissions to the neonatal intensive care unit were not significantly different in the two groups.

Conclusions: Patients having an intrapartum assessment of AFI as a fetal admission test are significantly more likely to have abdominal delivery for presumed fetal distress. However, the decision-to-incision time is not decreased and the perinatal outcome is not improved if the status of AF volume is known for patients in early labor.