ACCURACY OF ULTRASONOGRAPHY IN EVALUATING AMNIOTIC-FLUID VOLUME AT LESS-THAN 24 WEEKS GESTATION

The purpose of this investigation was to evaluate the accuracy of comm on sonographic techniques in assessing the amniotic fluid volume in pr egnancies of less than 24 weeks' gestation. Patients at less than 24 w eeks' gestation undergoing an amniocentesis for the placement of prost aglandin F-2 alpha for termination (because of genetic or fetal anomal ies, or both) were assessed for amniotic fluid volume. All fetuses wer e alive at the time of prostaglandin instillation. The amniotic fluid index and two-diameter pocket were used to determine the amniotic flui d volume. Prior to the prostaglandin instillation, the amniotic fluid volume was determined with para-aminohippurate using a diazo dye react ion with spectrophotometric analysis. The amniotic fluid volume was de termined in 21 pregnancies between 15 and 24 weeks' gestation, yieldin g volumes ranging from 189 to 1840 mi. Using published standards for a mniotic fluid volume in singleton pregnancies, oligohydramnios was pre sent in three gestations, the volume was found to be normal in 15 and hydramnios complicated three pregnancies. The two-diameter pocket iden tified the amniotic fluid volumes correctly more often (18 of 21 [85.7 %]) than the amniotic fluid index (10 of 21 [47.6%]) (P = 0.02). Norma l amniotic fluid volume was identified in nine of 15 (60%) pregnancies by the amniotic fluid index and in 14 of 15 (93.3%) by the two-diamet er pocket (P = not significant). Abnormal amniotic fluid volumes, olig ohydramnios, and hydramnios were recognized more often by the two-diam eter pocket (66.7%) than by the amniotic fluid index (1 of 6 [16.7%], P = not significant).