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. (Am J Obstet Gynecol 1999;180:1438-41.)