Direct prediction of amniotic fluid volume in the third trimester by 3-dimensional measurements of intrauterine pockets: a tool for routine clinical use.

Abstract

To develop an ultrasonographic technique for direct prediction of amniotic fluid volume. While women with near-term pregnancies were in the supine position, the intrauterine space was divided into 2 hemispheres and each hemisphere was further subdivided into 3 segments. The maximum distances along the 3 axes of amniotic fluid pocket in each segment were measured, and the volume was calculated as a half-ellipsoid or a crescent-cylinder. A sum of these calculations (prediction of amniotic fluid volume [pAFV]) was made and correlated with amniotic fluid volume measured at delivery (mAFV). In 714 deliveries, a high correlation coefficient of 0.896 between mAFV (mean +/- SD, 296.5 +/- 199.2 mL; range, 20 to 1480 mL) and pAFV (mean +/- SD, 300.2 +/- 180.8 mL; range, 27 to 1262 mL) was obtained. The regression equation was mAFV = 0.968pAFV + 8.68. The regression equation suggested that pAFV could be a direct predictor of intrauterine amniotic fluid volume in the third trimester.