MORTALITY AMONG TWINS AFTER AGE-6 - FETAL ORIGINS HYPOTHESIS VERSUS TWIN METHOD

Objective-To test the validity of the fetal origins hypothesis and the classic twin method. Design-Follow up study of pairs of same twins in which both twins survived to age 6. Setting-Denmark. Subjects-8495 tw in individuals born 1870-1900, followed through to 31 December 1991. M ain outcome measures-Mortality calculated on a cohort basis, Results-M ortality among twins and the general population was not significantly different except among females aged 60-89, in whom mortality among twi ns was 1.14 times (SE 0.03) higher than in the general population, Mor tality among female dizygotic twins was 1.77 times (0.18) higher than among monozygotic twins at age 30.59. Otherwise, mortality for monozyg otic and dizygotic twins did not consistently differ after age 6. Conc lusion-According to the fetal origins hypothesis the risk of adult mor bidity and mortality is heightened by retardation in intrauterine grow th. Twins, and in particular monozygotic twins, experience growth reta rdation in utero. The findings in the present study suggest that the f etal origins hypothesis is not true for the retardation in intrauterin e growth experienced by twins. Furthermore, the data are inconsistent with the underlying assumption of a recent claim that the classic twin method is invalid for studies of adult diseases. The present study is , however, based on the one third of all pairs of twins in which both twins survived to age 6. The possible impact of this selection can be evaluated in future studies of cohorts of younger twins with lower per inatal and infant mortality.