Prediction of small for gestational age newborns using ultrasound estimated and actual amniotic fluid volume: published data revisited.

Background: Intrauterine growth restriction (IUGR) is a complex problem in modern obstetrics. The presence of oligohydramnios is reported as an important diagnostic and prognostic factor in the management of a pregnancy complicated by IUGR.

Aim: To determine the predictive accuracy of sonographic and actual amniotic fluid volume (AFV) to identify small for gestational age (SGA; birthweight < 10%).

Methods: Before amniocentesis, the single deepest pocket (SDP) and amniotic fluid index (AFI) were obtained. The AFV was determined using a diazo-dye reaction. Thresholds for AFI, SDP and AFV were estimated using receiver-operating curves analysis and areas under the curves were used to assess predictive accuracy of these indices. Likelihood ratios (LR) were obtained.

Results: Among the 175 newborns, 16% had SGA. Compared to newborns with birthweight > 10%, all AFV indices were significantly lower (P= 0.001, P= 0.001 and P= 0.009 for AFI, SDP and AFV respectively) for SGA. The areas under the curves for all curves < 0.65 and the LR for all thresholds were < 5.0, reflecting poor diagnostic capabilities.

Conclusions: Despite observed lower AFV indices in SGA, neither sonographic examination nor determination of AFV is a reliable predictor of suboptimal growth.