Introduction The fetal insulin hypothesis proposes that the inverse relationship between birthweight and risk of diabetes and cardiovascular disease is partly as a result of inherited factors which influence the effect of insulin and insulin-like growth factors. It has been proposed that an inverse relationship between birthweight and parental risk of diabetes and cardiovascular disease is evidence in support of this hypothesis.
Patients and methods Data from a prospective birth cohort study, followed up to age 50, was used to assess the relationship between birthweight and reported parental diabetes, hypertension, angina and stroke using logistic regression.
Results Of the 832 cohort members traced at age 50, 574 (69%) returned questionnaires that included questions on parental illness. Complete data was available for 541 (94%) of these on maternal illness and for 531 (92%) on paternal illness. Birthweight, standardized for sex and gestational age and adjusted for social class at birth, was inversely associated with maternal stroke (odds ratio = 0.75, 95% confidence intervals 0.60–0.95). There were no other statistically significant associations between birthweight and risk of parental illness.
Discussion We found little evidence of a consistent inverse relationship between birthweight and parental risk of diabetes or cardiovascular disease. This may be because of the quality of our data—which is limited by the problems of collecting robust data over two generations.