Objective: The purpose of this study was to evaluate the relationship between duration of preterm premature rupture of membranes (PPROM) before delivery and development of respiratory distress syndrome (RDS).
Method: One hundred and fifty-nine cases of PPROM with gestational ages between 24 and 37 weeks and birth weights between 1300 and 2100 g were studied retrospectively, out of which, 61 infants developed RDS. Subjects with factors known to affect RDS such as: maternal diabetes; hemorrhage; hypertension; fetal asphyxia; multifetal pregnancies; abnormal presentations; or cesarean deliveries were excluded from this study.
Results: Out of 94 neonates, who had rupture of membranes (ROM) in less than 12 h, 41 cases (43.6%) developed RDS. Durations of ROM in 19 neonates were between 12 and 24 h and 6 of them (31.6%) developed RDS. In 21 cases whose ROM were between 24 and 48 h, RDS was seen in 4 (19%). However, in 25 subjects whose ROM was greater than 48 h, RDS presented in 10 cases. Statistical analysis, using Bartholomew's test, showed that there exists a reverse linear relationship between duration of ROM and RDS in the first 48 h. However, after 48 h, the risk of RDS increases, which may represent the effect of complications such as: chorioamnionitis; sepsis; and pulmonary hypoplasia on RDS.
Conclusion: Increasing the duration of PPROM, in the first 48 h, decreases the risk of RDS with a linear pattern.