The pattern of change in the lecithin/sphingomyelin ratio in patients with preterm premature rupture of membranes between 24 and 34 weeks' gestation

Objective: To report the pattern of change in the lecithin/sphingomyelin (L/S) ratio in patients with preterm premature rupture of membranes (PPROM) between 24 and 34 weeks' gestation. Study Design: L/S was determined prospectively using transvaginally and transabdominally collected amniotic fluid from patients with PPROM between 24 and 34 weeks' gestation. Samples were collected prospectively on admission and every 48 to 96 hours until L/S was ≥2.0. All patients received intramuscular betamethasone weekly. Results: Fifty-five patients were included in the study. One hundred twenty-seven samples were collected transvaginally and nine were collected transabdominally. Cox regression analysis showed that a higher initial L/S value and more advanced gestational age were associated with accelerated lung maturation. Among patients at ≥ 29 weeks' gestation with an initial L/S of ≥ 1.5 and <2.0 (n = 17), 15 of 17 (88%) reached L/S≥2 at a mean of 3.1 ± 1.7 days (range 1.0 to 7.0 days). With an initial L/S of ≥ 1.0 and <1.5 (n = 16), 14 of 16 (88%) patients reached L/S≥2 at a mean of 4.1 ± 1.9 days (range 1.7 to 7.0 days). With an initial L/S of <1.0 (n = 11), 6 of 11 (54%) patients reached L/S≥ 2 at a mean of 5.0 ± 1.6 days (range 4.7 to 6.8 days). Conclusion: Our data document a dramatic acceleration of fetal lung maturation among patients with PPROM at ≥29 weeks.