Obstetric ultrasound Archives - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: to evaluate the association between the variability of amniotic fluid index (AFI) values with gestational age and some sociodemographic and obstetric variables among low-risk pregnant women. METHOD: a comparative study was carried out including 2868 low-risk pregnant women who had routine obstetric ultrasound examination, including fetal biometry and the measurement of AFI, from 20 to 42 weeks of gestation. The data were analyzed using Student's t test, analysis of variance of mean AFI values along gestational ages, according to other control variables, and also by multiple linear regression analysis. RESULTS: there was no significant variation of mean AFI values during the time of pregnancy neither when separately evaluating its association with maternal age, color, education, smoking habit, parity, and the presence of previous cesarean section scars, nor when the evaluation was performed through multivariate analysis. In this situation only the increase in gestational age showed to be associated with the decrease of AFI. Generally speaking, the mean AFI values fluctuated between 140 and 180 mm between the 20th and the 36th week, then showing values below 140 mm in a progressive decrease after this limit of gestational age. CONCLUSIONS: AFI values do not show a significant variation during pregnancy regarding the studied sociodemographic and obstetric variables.