Predictive value of sonographic examination to visualize retained placenta directly after birth at 16 to 28 weeks.

Abstract

A prospective study was performed to assess the predictive value of an ultrasonographic examination directly after a spontaneous birth at 16 to 28 weeks' gestation to exclude the possibility of retained placental tissue. The aim of this procedure is to prevent routine curettage, which can induce Asherman's syndrome, uterine perforation, and anesthetic complications. Over a 2 year period the clinical course in 64 women, who had been delivered of their infants at 16 to 28 weeks' gestation, was followed through 6 weeks post partum. Sonographic examination was performed within 30 min after delivery of the placenta independent of macroscopic judgment of completeness of placenta. The examination was classified into three categories (with subsequent clinical interpretation): sharp lining of echogenic uterine wall with translucent cavity (uterine cavity containing fluid blood), sharp lining of the wall with echogenic area in cavity not continuous with the wall (uterine cavity with blood clot), and irregular lining with echogenic area continuous with the uterine wall and extending into the cavity (uterine cavity containing retained placental tissue). Women with sharp uterine lining without (n = 32) or with (n = 7) echogenicity in the cavity had no direct operative removal of placental tissue; 3 underwent curettage at a later stage (17, 18, and 34 days, respectively). A direct digital removal of placenta or curettage was performed on 25 women who revealed echogenicity continuous with the uterine wall. The 25 of 28 operatively obtained tissues were examined microscopically for trophoblasts. The sensitivity of the sonographic examination to find retained placental tissue was 85% (17 of 20) at 95% confidence intervals of 62 to 97%, the specificity was 88% (36 of 41) at 95% confidence intervals of 74 to 96%, and there were 25% (5 of 20) false positive judgments and 8% (3 of 39) false negative judgments. The positive predictive value of ultrasonography to find retained placenta of 68% (17 of 22) at 95% confidence interval of 55 to 92% combined with the negative predictive value of 92% (36 of 39) is sufficient to strongly suggest that curettage should not be performed routinely in these pregnancies at high risk for retained placental tissue.