Should assessment of amniotic fluid volume form an integral part of antenatal fetal surveillance of high risk pregnancy?

This study was conducted to evaluate the role of the Amniotic Fluid Index (AFI), used along with nonstress cardiotocography (NST) and fetal acoustic stimulation test (FAST), when required, in prediction of adverse pregnancy outcome. Over a 3-year period 565 pregnant women had antepartum fetal surveillance due to various high risk pregnancy factors and delivered within 7 days of the test. Antepartum fetal surveillance included nonstress cardiotocography together with estimation of AFI. Need for induction of labour, presence of meconium at rupture of membranes, Caesarean section for fetal distress, Apgar score at 5 minutes, need for neonatal endotracheal intubation, admission to neonatal special care unit and perinatal death were the main outcome measures. Nonreactive nonstress tests and Caesarean sections for fetal distress were more common and neonatal outcome was significantly poorer in patients with AFI < 5 cm than in those with higher AFI values. Of the 4 perinatal deaths in the group with AFI < 5 cm, 3 had a reactive NST within 7 days of fetal death. It is concluded that pregnancy outcome is often poor in the presence of very low AFI and in these cases a reactive NST loses its usual reassuring value. It is suggested that AFI estimation should be included as an integral part of antepartum fetal surveillance of high risk pregnancies.