The benefits of antenatal steroids in multiple pregnancies is unclear and requires further research. Objective: To determine the effect of the use of antenatal steroids at current dosing levels on the incidence of Respiratory Distress Syndrome (RDS) in premature multiple gestation infants.Design and Method: A retrospective cohort study was conducted on infants with birth weights between 501 grams and 1500 grams enrolled in a computerised database at Womens College Hospital, Toronto, Canada, a regional perinatal unit, between January 1990 and December 1995. Outcome Measures: These were the occurence of RDS and the need for surfactant replacement therapy (Surfx) in relation to antenatal steroid status. Antenatal steroid therapy was defined as complete when delivery occurred more than 24 hours and less than 7 days after a dose of steroid. RDS was defined as a PaO2<50mm Hg in room air or requirement of oxygen to maintain PaO2>50mm Hg and a chest radiogram consistent with RDS. Results: 1201 infants were enrolled during the study period and after excluding congenital anomalies and incomplete steroid therapy 940 were available for study; 230 multiples and 710 singletons. There were no statistically significant differences in birthweight, gestation, sex or mode of delivery between the two groups. There was no reduction in the incidence of RDS in multiple gestation infants [OR=1.04, 95%CI(0.6-1.8)] but a significant reduction in singleton infants [OR=0.68, 95%CI (0.52-0.89)] after antenatal steroids. Log regression analyses was carried out to look for any confounders in the baseline variables studied. Multiple birth and race were effect modifiers and the effect size greatest in singleton black infants [OR=0.35, CI(0.18-0.73)].Conclusion: Antenatal steroid therapy does not reduce the incidence of RDS in multiple gestation infants. It is likely that a modification of the current dosage regimen is required in this group and warrants a comparative trial. Table

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