Sonographic detection of fetal intraperitoneal fluid.

The sonograms from 15 patients who underwent 40 intrauterine transfusions at the University of California San Francisco School of Medicine, between December 1981 and December 1984 were retrospectively reviewed. The authors found that 12 to 14 ml of fluid were easily seen in 18‐ to 20‐menstrual‐week fetuses and that 30 to 40 ml were seen in fetuses at greater than or equal to 30 menstrual weeks. Since the study was retrospective, the absolute minimum of detectable fetal intraperitoneal fluid was not recorded for each fetus. The above represent amounts that were consistently documented during each intrauterine transfusion. In order to gain information about the minimum detectable fetal intraperitoneal fluid, two fetuses undergoing intraperitoneal transfusions were studied prospectively. The minimum fetal intraperitoneal fluid volumes observed were 10 ml in a 22‐week fetus and 15 ml in a 26‐week fetus.