The relationship of fetal plasma protein concentration and hemoglobin level to the development of hydrops in rhesus isoimmunization.

Fetoscopic samples of pure fetal blood were obtained at 18 to 25 weeks' gestation from seven hydropic and 10 nonhydropic fetuses affected by rhesus isoimmunization, and the fetal plasma albumin, plasma total protein, and hemoglobin concentrations were determined. All fetuses with sonographic evidence of hydrops had a hemoglobin of 3.8 gm/dl or less, whereas all but one of those without hydrops had a hemoglobin greater than 4.0 gm/dl. The plasma total protein was less than 2 standard deviations below the mean of the normal range in all hydropic fetuses and in six of 10 of those without hydrops. Hypoalbuminemia was found in six of the seven hydropic fetuses and in two of the nonhydropic fetuses. Ascitic fluid total protein and albumin concentrations were also determined in four hydropic fetuses, and the values in three were found to be more than 50% of the corresponding plasma levels.