Birth weight and age at menopause in Australian female twin pairs: exploration of the fetal origin hypothesis

In a twin sample where duration of gestation can be controlled, a specific example of the fetal origins hypothesis concerning association between low birth weight and early age at menopause is explored. The hypothesis is base d on the physiologically plausible path from intrauterine growth retardatio n and reduced numbers of primary follicles to an earlier menopause. The sam ple comprised 323 Australian female twin pairs where both co-twins had reac hed menopause naturally and reported on their weight at birth. Regression a nalysis showed no linear association between the two variables (P = 0.371, r(2) = 0.0009). Intra-pair differences in age at menopause were investigate d in the context of relative birth weight of co-twins. In 265 pairs an intr a-pair birth a eight difference was reported. In monozygotic (MZ) pairs (n = 168) this allowed for control of genetic effects as well as gestation dur ation. No significant differences dependent on birth weight relative to co- twin were found for age at natural menopause in either MZ or dizygotic (DZ) twin pairs, even in pairs whose birth weights differed markedly. There was some indication that twins with premature ovarian failure were heavier at birth than twins with normal or later menopausal age. We conclude that the hypothesis that lower birth weight is associated with earlier menopause is not supported by our data.