Seasonality in Down's syndrome. An endocrinological explanation
Janerich, D.T.; Jacobson, H.I.
Lancet 1(8010): 515-516
1977
ISSN/ISBN: 0140-6736 PMID: 65613 Document Number: 110708
In a report on time-series analysis of Down syndrome, Harlap showed a strong bimodal seasonal trend in the birth incidence of this congenital malformation. The cause of the seasonality was not noted. It is proposed that the cause of this seasonality, and the underlying cause of Down syndrome, is the status of the mother's endocrine system during the meiotic divisions which take place just before conception. The evidence for this conclusion comes from epidemiological and clinical studies which show that exogenous hormones taken by the mother before pregnancy can cause chromosome abnormalities in the zygote; and that seasonal tissue changes occur in the estrogen target cells of the female endocrine system, these changes coinciding seasonally with the conception of fetuses with Down syndrome. The data indicate minimum rates of Down syndrome conceptions in early spring and early autumn. In populations where Down syndrome shows seasonality, planning conceptions for low-risk periods could reduce the risk.