Sex determination and stress

Women who endure a very stressful event in their families around the time of conception have an increased chance of giving birth to a baby girl. Dorthe Hansen and colleagues at the John F Kennedy Institute in Glostrup, Denmark, took a look at national fertility records of Denmark. They studied 3,072 mothers who had gone through either a death in the family or a hospitalisation of a family member because of cancer or a heart attack during the year their baby was born or the previous year. They found that 49 per cent of the babies in this group were boys, as compared to over 51 per cent in mothers who had not suffered a stressful event. The percentage of boys was lowest (40-43 per cent) when the stressful event occurred during the first trimester of pregnancy. Stressed parents are better off producing a girl as their survival chances are better than boys ( British Medical Journal , Vol 319, No 7209).

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