Amniotic fluid prealbumin as a potential marker of fetal abnormalities.

Normal amniotic fluid prealbumin (PAB) levels between 16 and 41 weeks of pregnancy are demonstrated in 175 samples from various gestational ages. PAB was measured quantitatively by immunonephelometry and qualitatively estimated by electrophoresis while total protein content was measured by colorimetry. The percent of PAB values in the total protein content is inversely correlated to the gestational age. Fetal abnormalities and abnormal conditions in pregnancy diagnosed in the second trimester and early third trimester (16-32 weeks) show significantly (p < 0.01) higher than expected PAB values (25.9 +/- 4.6 mg/l, range 19.5-35.6, n = 23) in comparison to normal fetuses and normal pregnancies of the same age (13.6 +/- 3.6 mg/l, range 4.3-19.8, n = 87). The remaining 65 samples of normal third trimester amniotic fluid were evaluated in comparison to the second trimester normal values, and inverse correlation in respect to advancing pregnancy was observed. PAB values were corrected for the total protein content and the resulting ratio had the lowest variation compared to PAB and total protein values. It is proposed that PAB, although not specific for a particular disorder, expressed as a ratio of the total protein content is a potential biochemical marker for certain fetal defects and complications of pregnancy.