A baby is twice as likely to be born bottom-first if either or both of its parents themselves were also "breech" deliveries, according to a paper released on Friday by the British Medical Journal (BMJ).
Fewer than five percent of births are breech delivery, which carries higher risks of mortality and health problems for the infant than for head-first births.
The known risk factors for breech births include if the baby is the mother's first child or if the mother has a contracted pelvis, is of high maternal age or has a uterine abnormality. What has been unclear, though, is whether there could be a genetic link.
Investigators from the University of Bergen in Norway pored over data for all the births in Norway between 1967 and 2004 and compared this with all the information available on men and women and their first-born children.
Pooled together, the datasets amounted to 232,000 mother-child comparisons and 154,000 father-chld comparisons.
The researchers found that men and men and women who had been breech-delivered ran more than twice the risk of breech delivery in their own first pregnancies. The risk was the same for men and women alike.
In addition, babies that had been delivered naturally, rather than by caesarean, were at the biggest risk of a breech delivery.
In an editorial, the BMJ said the research was interesting. But, it cautioned, more evidence was needed of a genetic link before doctors warned mothers of a higher risk of breech delivery if their parents had also been born bottom-first.