Fetal lung maturation in twins: a study of tracheal aspirates

In 10 pairs of twins born at 36-40 wk gestation lung maturity was evaluated immediately after delivery by means of an analysis of their tracheal aspirates. The foam-stability test was performed by the method of Clements in all newborns within 5 min of their birth. In 6 pairs of twins the lecithin/sphingomyelin ratio was also determined, using the Gluck method. In all pairs the foam test was positive in greater dilution in the first twin than in the second. In spite of these differences not one of those newborns with positive foam tests showed evidence of respiratory distress, even when the test was positive in the smallest dilution. In the second twins of 2 pairs the foam test was negative in all dilutions. The L S ratios in these babies were 1.8 and 1.6, respectively. Both of them showed transient signs of respiratory distress syndrome shortly after delivery. These differences in lung maturity may possibly be attributed to earlier lung maturation due to greater stress in the firstborn of multiple pregnancies. This stress may cause increased secretion of glucocorticosteroids from fetal adrenals with an accelerating effect on fetal lung maturation. It is possible that this simple and safe procedure for evaluating lung maturity in the newborn is indicated in all such newborns who are prone to or are at special risk of respiratory distress syndrome, such as in multiple pregnancy.