Prediction of fetal lung maturity by amniotic fluid fluorescence polarization, L:S ratio, and phosphatidyl glycerol.

The relation of amniotic fluid fluorescence polarization (FP) to fetal lung maturity was examined in 186 pregnancies terminating within 48 hours of the fluid collection. Among the 9 babies who developed hyaline membrane disease (HMD), 8 were associated with FP values of 0.340 or more, and 1 had an FP value of 0.329. In 95 of these patients, the lecithin:sphingomyelin (L:S) ratio and the presence or absence of phosphatidyl glycerol (PG) were also determined. All 9 infants with HMD had L:S ratios less than 2.00 and no PG detectable in the amniotic fluid. Using an FP value of 0.325 or less, an L:S ratio of 2.00 or more, and the presence of PG as criteria for lung maturity, FP, L:S ratio, and PG did not differ significantly in the number of false predictions of HMD. Each test detected some mature infants who would have been incorrectly classified by at least 1 of the other tests. The status of all infants born at 33 weeks' gestation or later who did not develop HMD would have been correctly predicted by FP, L:S ratio, or both. These 3 tests, therefore, are complementary and can be used in combination to reduce the number of false predictions of HMD.