The purpose of this study was to determine the superior technique, if either, of the amniotic fluid index (AFI) vs the single deepest pocket technique in predicting an adverse pregnancy outcome among high-risk patients undergoing antenatal testing.

Patients having modified biophysical profile (nonstress test plus sonographic estimation of amniotic fluid) were randomized to either have AFI or determination of the presence or absence of a 2 × 1-cm single deepest pocket.

Between January of 1997 and December of 2001, 1080 women were randomized with 530 women in the AFI arm, and 558 in the 2 × 1 pocket arm. The maternal demographics and prenatal complications were similar between groups. Significantly more patients were identified as having oligohydramnios using AFI (17%) compared with using 2 × 1 pocket (10%) (P=.002). The overall rate of cesarean section for nonreassuring fetal heart rate (FHR) tracing was 3.8% (30 cases, with 16 cases in the AFI-monitored, and 14 cases in the 2 × 1 pocket–monitored groups, respectively, P=.608). Logistic regression analysis showed no difference between the groups with respect to the ability to identify patients who underwent cesarean section for nonreassuring FHR tracing during labor (P=.999). The umbilical artery pH <7.1 (P=.688) and admission to the newborn intensive care unit were also comparable between groups.

During antepartum fetal surveillance, use of single deepest pocket compared with amniotic fluid index is associated with a significantly lower rate of suspected oligohydramnios.