Amniotic fluid beta-2-microglobulin in normal and complicated pregnancies. Correlation with gestational age, creatinine concentration and L/S ratio.

The beta-2-microglobulin concentrations in 127 aminotic fluid samples, obtained during weeks 32-42 of normal pregnancies (n = 58) and complicated pregnancies (n = 69), were measured and correlated with gestational weeks, amniotic fluid creatinine concentrations and L/S ratios. A significant (p less than 0.001) decrease of beta-2-microglobulin concentration occurred from week 32 to 34 of normal pregnancies, after which the beta-2-microglobulin level was unchanged. There were no significant correlations between beta-2-microglobulin concentrations and amniotic fluid creatinine concentrations of LK/S ratios. The beta-2-microglobulin content was elevated in samples obtained from diabetic and toxemic pregnancies. Measurement of beta-2-microglobulin in amniotic fluid seems to be of limited value for determining fetal age, but it may be useful in estimating fetal renal maturity.