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Respiratory distress syndrome in twins.

SUMMARY Respiratory distress syndrome occurred in 77 of 1,130 liveborn twins (1 : 15) and appears to be more fre quent than in singletons. This increase cannot be entirely accounted for by the higher prematurity rate of twins over singletons. In 46 twin pairs with at least one affected, there was a significantly higher concordance rate among MZ than DZ pairs, suggesting that genetic factors are of some etiologic importance in this disease.