Evaluation of fetal lung maturity in diamniotic twins.

OBJECTIVE: This study was undertaken to evaluate the correspondence in fetal lung development between diamniotic twins.

STUDY DESIGN: Lecithin/sphingomyelin ratios were determined for amniotic fluid specimens collected from each sac in 58 diamniotic twin pregnancies.

RESULTS: Overall, the lecithin/sphingomyelin ratios of twin A and twin B and those of the larger and smaller twins of each pair were closely correlated (r >/= 0.83, P <.001). When stratified by gestational age, however, the percentage disparity in lecithin/sphingomyelin ratios between members of twin pairs was significantly greater at </=32 weeks' gestation (25%) than at >32 weeks' gestation (15%, P =.027). An analysis of the lecithin/sphingomyelin ratios of twins with a large lecithin/sphingomyelin ratio disparity (>/=20%) suggested that this disparity was a result of 1 twin having a lecithin/sphingomyelin ratio that was advanced for gestational age with respect to that of the co-twin. Disparities in lecithin/sphingomyelin ratio were not significantly affected by fetal sex or by discordance in size between the twins.

CONCLUSION: At relatively early stages of diamniotic twin gestation (</=32 weeks' gestation), lecithin/sphingomyelin ratios should be obtained for both amniotic sacs to ensure accurate assessment of fetal lung maturity in both twins.