Superiority of amniotic fluid index over amniotic fluid pocket measurement for predicting bad fetal outcome

Semiquantitative amniotic fluid volume (AFV) determination is a component of the fetal biophysical profile (BPP). To assess decreased AFV, we did BPPs of 174 fetuses within 1 week of delivery. Two methods were used: Measurement of the single largest vertical pocket (oligohydramnios = depth < 1 cm) and the four-quadrant amniotic fluid index (AFI) (oligohydramnios = AFI ≤ 5 cm). AFV, as determined by each method, was related to measures of fetal outcome (perinatal mortality, fetal distress, Apgar score, meconium-stained amniotic fluid, and intrauterine growth retardation [IUGR]). The AFI was more sensitive in predicting mortality (87.5%) and the following measures of perinatal morbidity: low 5-minute Apgar score (88.8%), fetal distress during labor (86.6%), meconium-stained amniotic fluid (63.6%), and the presence of IUGR (79.4%). The sensitivity of amniotic fluid pocket measurement of < 1 cm was 75%, 72.2%, 66;6%, 47.7%, and 55.8%, respectively, for the same measures. Using the AFI instead of a single pocket measurement in BPP assessment increased the sensitivity and positive predictive value of the BPP from 64.7% to 76.4% and from 45.8% to 68.4%, respectively. Our data suggest that qualitative AFV measurement using the AFI.