How Well Do the Popular Ultrasonic Techniques Estimate Amniotic Fluid Volume and Diagnose Oligohydramnios, in Fact?

The aims of the study were to compare the different estimation methods for the diagnosis of oligohydramnios and to determine concordance between estimated amniotic fluid volume (AFV) measured by ultrasonography and actual AFV measured directly. Another purpose was to investigate the effect of oligohydramnios on neonatal outcome. This study was done at a tertiary care center. The participants were scheduled between 37 and 40 weeks for cesarean delivery. Estimated AFV was ultrasonographically assessed, and then actual AFV was directly measured during the cesarean delivery to compare the subjective method (SM), amniotic fluid index (AFI), single deepest pocket (SDP), and 2-diameter pocket. Totally, 138 patients were included in the present study. Of 35 (34%), 24 (21%), 12 (9.5%), and 10 (7.8%) were defined as oligohydramnios by the SM, AFI, SDP, and 2-diameter pocket, respectively. The number of patients with actual oligohydramnios was 35 (34%). Most authors suggest as a method use of the SDP more than the AFI, because of overmanagement through the AFI. However, this study, which was conducted using both nonprejudiced and criterion-standard methods, showed that the SM and AFI technique were more successful to estimate oligohydramnios than other methods. Also, adverse pregnancy outcome was not closely associated with isolated oligohydramnios.