Respiratory distress syndrome in twin infants compared with singletons

Objective: The purpose of this study was to determine gestational age-specific incidence and risk factors of respiratory distress syndrome (RDS) in twins compared with singletons. Study design: An analysis of 850,406 singleton and 23,278 twin infants born alive in Finland between 1987 and 2000 was performed. A number of antenatal and perinatal/intranatal factors were evaluated. Results: At less than 28 weeks of gestation, the incidence of RDS was higher in both first- and second-born twins compared with singletons. At more advanced gestation, first-born twins had a significantly lower incidence of RDS compared with the others. There was no difference in the concordance of RDS between same-sex and opposite-sex twin pairs. Vaginal delivery, female sex, being born first, and being the lighter of the twins protected from RDS. Conclusion: After taking into account gestation, twins are not at higher risk of RDS compared with singletons except at very early gestation. Environmental factors predominate over genetic ones in the predisposition to RDS in twins. (C) 2004 Elsevier Inc. All rights reserved.