Fetal lung maturation in twin gestation.

Clear amnionic fluid was collected at cesarean section and the lecithin/sphingomyelin (L/S) ratio was used to evaluate fetal lung maturation in 42 twin gestations. The L/S ratios of twin pairs were usually similar in both numerical value and predictive accuracy except when the greater L/S ratio from one member of a pair indicated borderline lung maturity. Twin fetal lung maturation was found to be independent of sex, zygosity, and birth weight discordance. Comparison of mean L/S ratios in twins to those of uncomplicated singleton pregnancies revealed that fetal lung maturation occurred several weeks earlier in twins.