[Mortality among twins after the age of six: the programming hypothesis versus the twin-method]

According to the foetal-origins hypothesis the risk of adult morbidity and mortality is heightened by intrauterine growth retardation. Twins, and in particular monozygotic twins, experience growth retardation in utero. A total of 8495 twin individuals born 1870-1900 in Denmark were followed through 1991 and death rates were calculated on a cohort basis. Deaths rates for twins and the general population were not significantly different except for females aged 60-89: mortality for female twins in this age group was 1.14 times (SE 0.03) higher than the general population. Female dizygotic twins experienced death rates 1.77 times (SE 0.18) higher than monozygotic twins at ages 30-59. Otherwise, mortality for monozygotic and dizygotic twins did not consistently differ after age six. The findings in the present study suggest that the foetal-origins hypothesis is not true for the intrauterine growth retardation experienced by twins.