Amniotic fluid index in twin gestation

This study was performed to describe a methodology for a two-pocket amniotic fluid index (AFI) for each fetus of a twin gestation. Data included 216 pairs of measurements that were analyzed to yield regressions (curves) for all observations, as well as for the larger and smaller AFI of each observation on a particular set of twins. The twin AFI increased non-linearly until week 27. From week 27 to week 36, decreasing linear trends were found. Measures of intrasonographer, intersonographer, within-mother and between-mothers variation are reported. The estimates of variation were used to plot confidence limits for all three curves.