Risk of intra-amniotic infection/inflammation and respiratory distress syndrome according to the birth order in twin preterm neonates.

Objective: Prior studies have suggested that nonpresenting twins are more likely to develop respiratory distress syndrome (RDS) than presenting twins. While the underlying mechanism is not known, exposure to intra-amniotic infection/inflammation (IAI) has been associated with a reduced risk of RDS in singleton gestations. In the current study, we compared the risk of RDS in preterm twin neonates according to birth order with adjustment for the presence or absence of IAI.Methods: The study population consisted of consecutive twin neonates who delivered ≤35 weeks and underwent amniocentesis within 7 days of delivery. The frequency of RDS and IAI was compared between presenting and nonpresenting twin pairs. Amniotic fluid (AF) was cultured for aerobic/anaerobic bacteria and genital mycoplasma. IAI was defined as a positive AF culture or an AF white cell count ≥19/mm3.Results: A total of 120 twin pairs were enrolled. Compared with presenting twins, nonpresenting twins had a lower risk of IAI (36 vs. 26%, respectively, p < .05), but a higher risk of RDS (18 vs. 25%, respectively, p < .05). In multivariate analysis, only IAI remained significantly associated with RDS (OR 0.18, 95% CI 0.05-0.65), whereas birth order was not.Conclusions: In preterm twin neonates, the increased risk of RDS in nonpresenting twins is likely due to lower exposure to IAI and not birth order.