Breech deliveries 'inherited'

A baby is twice as likely to be born bottom first if either or both parents were themselves breech deliveries, indicating the position is inherited, a study said.

The vast majority of babies are born head first and fewer than one in 20 are the other way round, researchers in Norway found.

Such deliveries carry significantly greater risks for babies, who are more likely to die or suffer from health problems, the British Medical Journal, which is publishing the study said.

Researchers from the University of Bergen looked at data covering all the births in Norway between 1967 and 2004. They studied the information available on men and women and their first born children - a total of 387,555 parent and child units.

They found that men and women who had been delivered full-term in the breech position had more than twice the risk of breech delivery in their own first pregnancies. Babies delivered naturally, not by caesarean, were at the biggest risk of a breech delivery.

The risk was equally strong for male and female parents. And results were emphasised when researchers studied the 35,056 men who had children with two different women.

The authors suggested that genes predisposing to a breech delivery are transferred to the foetus which then increases the risk of the mother having a breech delivery.

Factors such as premature delivery and low birth weight were also known risk factors associated with a breech delivery. But these only account for up to one in seven of all such breech births, said the study, published ahead of print on bmj.com.

Breech delivered parents, born prematurely, were found to have no increased risk of breech delivered offspring - the result of being premature rather than genes predisposing towards a breech delivery.

Despite the suggestion of a genetic trait for breech presentation some of the results suggest an environmental factor or interaction, the researchers added. They said that further investigation was needed before advising mothers of a high risk of breech delivery if they themselves had been breech babies.

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