Amniotic fluid L/S ratio in twin gestation.

Transabdominal amniocenteses were performed on both sacs of 14 sets of twins. In each instance one sac was marked with methylene blue to correctly identify the fluids. The lecithin/sphingomyelin ratio was determined on each fluid, and the correlation coefficient between the two sets of fluids was 0.86. There was no significant difference in the fluids' L/S ratios. The importance of this in terms of understanding the variables affecting fetal lung maturation and in clinically managing twin pregnancies is stressed.