Baby girls whose mothers smoke during pregnancy may face fertility issues later in life, scientists say.
Researchers suggest that girls born to mothers who did not put down the cigarettes while pregnant exhibit signs of increased testosterone exposure.
They say this may affect their hormone and reproductive function.
The study presented at the European Society for Paediatric Endocrinology meeting in Vienna, Austria, suggests cigarettes are an endocrine disruptor – meaning they interfere with hormone systems.
In this instance, the scientists say they can masculinise girls in the womb.
They add that daughters of women who smoked during pregnancy may suffer from hormonal and reproductive health problems in the long term.
Dr Deniz Ozalp Kizilay and colleagues at Cigli State Training Hospital in Turkey measured Anogenital distance (AGD) – the distance from the midpoint of the anus to the genitalia – which is regulated by testosterone levels during foetal development.
They looked at 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.
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.”
Smoking during pregnancy is widely accepted to be bad for the health of both the mother and baby.
Scientists say girls exposed to higher levels of male hormone testosterone in the womb are at greater risk of abnormal development and long-term negative effects on their fertility and metabolism.
However, Dr Kizilay warns that the mechanisms behind the potential reproductive problems caused by exposure to cigarette smoke in the womb are not fully understood.
He added: “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 plans to monitor the long-term effects of exposure to higher testosterone levels caused by smoke exposure in the same group of baby girls, to assess how this may affect their future health and fertility.
Dr Kizilay concluded: “To our knowledge, this is the first time that the unfavourable effects of prenatal smoke exposure on AGD, as a marker of testosterone exposure, has been demonstrated in female newborns.
“These findings are a valuable contribution to our better understanding of the intergenerational effects of maternal smoking.”