Genetic influences in respiratory distress syndrome: a twin study

This is a twin study of the contribution of genetic influences on the pathogenesis of respiratory distress syndrome (RDS). Retrospectively, the files of twins born between 1976 and 1995 in the Academic Medical Centre (before Wilhelmina Gasthuis) of the University of Amsterdam were studied with a gestational age of 30 to 34 weeks and 1 or both with RDS. Data were collected on gestational age, birth weight, Apgar score, or diabetes in the mother as risk factors. All children were born vaginally. One hundred ninety-four pairs of twins were born with a gestational age of 30 to 34 weeks. Twenty-six pairs were excluded, because neither of the babies developed RDS. Of the 168 pairs, we were able to determine zygosity in 80 pairs, of which 18 were monozygotic and 62 were dizygotic twins. This is a normal ratio for the gestational age of 30 to 34 weeks. Risk factors as formulated above were not different between the monozygotic and dizygotic twins. RDS occurred more frequently in both twins when the twins were monozygotic (12 of 18, 67%) than when the twins were dizygotic (18 of 62, 29%). This difference was statistically significant, P < .05 by Chi square analysis. When only 1 twin developed RDS, it was the second born in 4 (67%) of the other 6 pairs of monozygotic twins and in 34 (77%) of the 44 dizygotic twins (77%). This twin study supports the notion of a genetic contribution to RDS.