Standardized measurement of amniotic fluid volume by correlation of sonography with dye dilution technique.

Amniotic fluid volume was measured in two ways in 23 subjects admitted for interruption of pregnancy at gestational ages 16-24 weeks. The amniotic fluid volume calculated from sonographic measurements was plotted against the "true" amniotic fluid volume obtained by a dye dilution technique. Linear regression analysis showed a good correlation between the two methods (r = 0.815; P less than .001) and yielded a factor that may be used on a general basis to derive the true amniotic fluid volume from the value obtained by sonography. This approach thus offers a standardized procedure for amniotic fluid volume estimation in the second trimester based on the technical simplicity of ultrasonography with the relative accuracy of the dye dilution technique.