Predicting concordance of biochemical lung maturity in the preterm twin gestation

Abstract

Objective: To propose a strategy for lung maturity amniocentesis in diamnionic twin gestations by exploiting indicators of concordance of lung maturity status. Methods: Amniotic fluid from 92 diamnionic twin gestations was assayed for lung maturity by standard methodology. The rates of concordance of lung maturity status between twins were calculated after stratification by gestational age, chorionicity, gender and weight discordance. Results: At the extremes of gestational age (28, 29, 36 and 37 weeks), twins are 100% concordant in lung status; for twins of 33-35.9 gestational weeks, lung concordance is significantly lower at 0.91 (p = 0.02); for 30-32.9 weeks, a rate of 0.52 is even lower (p = 0.001). Same-gender twin pairs of 33-35.9 weeks and twin pairs with estimated fetal weight discordance exceeding 20% or less than 10% were uniformly concordant in their lung maturity. Conclusion: Non-selective single amniocentesis may be performed if the gestational age is greater than 35.9 weeks. Double amniocentesis should be performed in the following: twins of 30-32.9 gestational weeks and twins of 33-35.9 weeks unless the twin pair is gender-concordant, or calculated fetal weight discordance is less than 10% or greater than 20%.