Severe life events may lower the sex ratio

Exposure to floods and earthquakes is associated with a lower proportion of male to female children conceived at the time of the disaster. To test the hypothesis that exposure to severe life events before conception might also reduce the sex ratio Hansen et al studied all births to Danish women in 1980-92 (p 548). They identified 3072 pregnancies where the mother's partner or children had been admitted to hospital with cancer or myocardial infarction or had died in the year of birth or previous year. The proportion of boys was 49.0% in the exposed group and 51.2% among controls. The nearer the exposure was to conception, the lower the sex ratio.

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Relevant Article

Severe periconceptional life events and the sex ratio in offspring: follow up study based on five national registers

Dorthe Hansen, Henrik Møller, and Jørn Olsen
BMJ 1999 319: 548-549. [Full Text] [PDF]