Amniotic fluid volumetry by three-dimensional ultrasonography during the first trimester of pregnancy.

In a longitudinal prospective study, we quantitated the amniotic fluid volume (AFV) of 25 normal fetuses by endovaginal 3-D ultrasonography (3D-US) from the 8th to the 11th week of pregnancy. AFV by 3D-US was obtained by subtracting the volumetric measurement of the embryo (EV) from the amniotic sac volume (ASV). EV and ASV were obtained by virtual organ computer-aided analysis (VOCAL), using 6 degrees of rotation. AFV increased from 5.75 to 42.96 cm(3) from the 8th to the 11th week (ANOVA, p < 0.05), with a correlation between gestational age and AFV (p < 0.001, r(2) = 98.1%). We conclude that there was an increase in AFV assessed by 3D-US. The AFV values for normal fetuses can be used for comparison with those detected in pregnancies with risk of fetal loss.