Intrapartum amniotic fluid volume at term. Association of ruptured membranes, oligohydramnios and increased fetal risk.

The amniotic fluid index (AFI), a semiquantitative technique for assessing amniotic fluid volume, has been shown to be a useful adjunct in antepartum surveillance. We evaluated the usefulness of the AFI in the early intrapartum period as it relates to subsequent fetal morbidity and fetal heart rate patterns. Two hundred term gravidas presenting in the latent phase of labor with vertex-presenting fetuses were studied. An intrapartum AFI less than or equal to 5.0 cm was associated with a significant increase in the risk of cesarean section for fetal distress and of an Apgar score of less than 7 at one minute as well as abnormal fetal heart rate patterns in late labor. The majority (71.4%) of the patients with an intrapartum AFI less than or equal to 5.0 cm had ruptured membranes on entry; however, there was no significant difference in outcome when they were compared to patients with intact membranes and oligohydramnios. Variable decelerations on entry were associated with oligohydramnios in 43.8% of the patients. An AFI less than or equal to 5.0 cm in the early intrapartum period is a risk factor for perinatal morbidity and abnormal fetal heart rate patterns in subsequent labor, and ruptured membranes in early labor are a risk factor for oligohydramnios.