Smokers less likely to give birth to boys

Smoking in pregnancy reduces the chance of a woman giving birth to a son, says a UK study.

The link could explain the significant decline in the male-to-female sex ratio seen in birth registries over the past few decades, say the researchers.

Passive smoking also appears to have a detrimental affect.

Among 8,960 singleton births between 1998 and 2003, the male-to-female ratio was lowest at 0.67 when both parents smoked during the pregnancy. A male-to-female ratio of 1.21 was observed if there was no smoke exposure in pregnancy.

Presenting the findings at a meeting of the Royal College of Paediatrics and Child Health last week in York, the researchers said sperm carrying the Y chromosome may be especially susceptible to the effects of cigarette toxins.

Study lead Professor Bernard Brabin, from Liverpool School of Tropical Medicine, said: ‘This is a massive public health problem.’

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