Women who smoke during pregnancy may damage their daughters’ future chances of having a baby, warns a new study.

Researchers discovered that baby girls born to mothers who smoked while pregnant show signs of increased testosterone exposure, which may affect their hormone and reproductive function.

Their findings suggest that cigarettes are an endocrine disruptor that can “masculinise” girls in the womb and that daughters of women that smoked during pregnancy may suffer from long-term hormonal and reproductive health problems.

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Smoking during pregnancy is widely known to be bad for the health of both mother-to-be and baby, yet some women persist and many are exposed to second-hand smoke.

As well as the many toxins present in cigarette smoke, it is also suspected of having endocrine-disrupting properties that may increase testosterone levels.

Baby girls exposed to higher levels of the male hormone testosterone in the womb are at higher risk of abnormal development and long-term negative effects on their fertility and metabolism.

The researchers said that anogenital distance (AGD), the distance from the midpoint of the anus to the genitalia, is regulated by testosterone levels during foetal development, so is a sensitive marker of testosterone exposure and life-long reproductive health.

Dr Deniz Ozalp Kizilay and colleagues at Cigli State Training Hospital in Turkey, measured the AGD in 56 newborn girls and 64 newborn boys, from mothers who smoked during pregnancy.

AGD was “significantly” longer in the baby girls and correlated with the amount the mothers smoked. No effect was found on the AGD in the boys.

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Dr Kizilay said: “This significant increase in AGD in girls exposed to maternal smoking may be an indicator of excessive testosterone exposure that poses a risk for short and long-term health problems, including metabolism and fertility.

“Further investigation is needed to explain the relationship between maternal smoking, increased AGD and future health issues in girls.”

But Dr Kizilay said: “The mechanisms behind the potential reproductive problems caused by exposure to cigarette smoke in the womb are not fully understood.

“Our results do suggest that girls have higher testosterone exposure, but not how this relates to reproductive function.

“More extensive and carefully-designed studies are required to explain this relationship.”

The team now plan to monitor the long-term effects of exposure to higher testosterone levels caused by smoke exposure in the same group of baby girls.