COMPARATIVE EFFICACY OF 2 SONOGRAPHIC MEASUREMENTS FOR THE DETECTION OF ABERRATIONS IN THE AMNIOTIC-FLUID VOLUME AND THE EFFECT OF AMNIOTIC-FLUID VOLUME ON PREGNANCY OUTCOME

Objective: To determine in pregnant women with preterm labor the relat ive efficacy of the amniotic fluid index (AFI) and the two-diameter po cket to detect abnormalities in amniotic fluid volume (AFV), and to re late these findings to pregnancy outcome. Methods: Fifty-seven healthy women with preterm labor underwent amniocentesis in the third trimest er to detect subclinical chorioamnionitis and assess fetal lung maturi ty. The AFV was estimated by the AFI and two-diameter-pocket methods, then confirmed by a dye (aminohippurate sodium)-dilution technique. Ea ch labor was evaluated for severe variable decelerations requiring amn ioinfusion, fetal distress resulting in cesarean delivery, and a 5-min ute Apgar score below 7. Results: Using fluid volume confirmed by dye dilution, the AFI correctly diagnosed AFV as low (less than 500 mt) in only two of 23 (8.7%) patients, compared to 14 of 23 (61%) for the tw o-diameter pocket (P < .001). Fetal distress requiring cesarean delive ry occurred significantly more often in the hydramnios group (three of six) compared to those with normal AFV (one of 23) (P < .03), and app roached significance in the oligohydramnios group (two of 21) (P = .05 6). There were no significant differences among the three patient grou ps regarding the need for amnioinfusion for severe variable decelerati ons or the occurrence of 5-minute Apgar scores below 7. Conclusions: C ompared to the AFI, the two-diameter pocket is a superior sonographic measurement for the detection of oligohydramnios. In an otherwise low- risk pregnancy with preterm labor, oligohydramnios is associated with no greater risk for an adverse outcome than is a normal AFV.