Serial amniotic fluid index in severe preeclampsia: a poor predictor of adverse outcome

The purpose of the study was to determine the relationship between low amniotic fluid index and intrauterine growth restriction and nonreassuring fetal testing in patients with severe preeclampsia.

We reviewed the medical records of 136 women with severe preeclampsia managed conservatively for at least 48 hours. Patients were followed up with a daily nonstress test and amniotic fluid index. We evaluated amniotic fluid index < or = 5 cm and < or = 7 cm, measured on admission or just before delivery (i.e., final), and attempted to correlate these findings with the incidence of nonreassuring fetal testing necessitating cesarean section or the incidence of intrauterine growth restriction (birth weight < or = 10th percentile).

One hundred seven patients had a cesarean section, but only 42 (39%) of these were for a nonreassuring fetal heart rate tracing or a persistent biophysical profile of < or = 4, and 38 (36%) of the pregnancies resulted in infants with intrauterine growth restriction. During expectant management, the amniotic fluid index worsened for 61 (45%) patients and improved or remained the same for 75 (55%). For those with an amniotic fluid index of < or = 5 cm both on admission and at delivery, there was a significantly higher incidence of intrauterine growth restriction compared with those with an amniotic fluid index > 5 cm (p = 0.007 and p = 0.029, respectively). However, there was no association between intrauterine growth restriction and an amniotic fluid index < or = 7 cm. Moreover, there was no difference in the frequency of nonreassuring fetal heart rate testing on the basis of amniotic fluid volume (p = 0.59) or intrauterine growth restriction (p = 0.4).

For women with severe preeclampsia remote from term, an amniotic fluid index < or = 5 cm is predictive of intrauterine growth restriction but lacks sensitivity. There is no association between the amniotic fluid index status and frequency of cesarean section for fetal distress or nonreassuring fetal testing.