Breech Birth May Be Determined by Genes

'Bottom first' delivery more likely if either parent was born that way, study says

By Steven Reinberg
HealthDay Reporter

FRIDAY, March 28 (HealthDay News) -- If one or both parents were born bottom first or feet first -- called a breech delivery -- their children are twice as likely to be born the same way, Norwegian researchers report.

Most babies are born head first, but about one in 20 is born bottom first. Breech deliveries increase the risk that the baby will die or suffer from health problems, the study authors noted.

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"Both men and women delivered in breech presentation at term contribute to increased risk of breech delivery in their offspring," said lead researcher Tone Nordtveit, a research fellow at the University of Bergen. "Recurrence through the father is as strong as recurrence through the mother. Genes passed on from the father or the mother seem to be closely related to breech delivery," she added.

The findings were published in the March 28 online edition of the British Medical Journal.

For the study, Nordtveit's team collected data on all births in Norway between 1967 in 2004. Specifically, they looked at information on first-born children.

"Men and women who themselves were delivered in breech presentation had more than twice the risk of breech delivery in their own first pregnancies compared with men and women who had been cephalic presentations," Nordtveit said.

The strongest risks for breech delivery were found for vaginally delivered babies and were equally strong for men and women. Increased risk of recurrence of breech delivery in offspring occurred only for parents delivered at term, Nordtveit said.

When the researchers looked at 35,056 men who had children with two different women, they found the same risk for breech delivery, indicating that the increased risk appears to have a genetic component.

Predicting a breech delivery is important, Nordtveit said, because these deliveries are associated with increased mortality and morbidity.

"A considerable number of breech presentations are not detected before labor, despite careful antenatal surveillance," Nordtveit said. "To avoid undiagnosed breech deliveries, information about the mother's and the father's own presentation at birth will be valuable in the evaluation of fetal presentation in the third trimester."

Janet Hardy, an assistant professor of obstetrics/gynecology and pediatrics at the University of Massachusetts Medical School, agrees that knowing the parents' history of breech delivery may help predict the risk of their child having a breech presentation.

"Little is known about risk factors for breech presentation, and the idea that birth position might be inherited from either or both parents is novel," said Hardy, who authored an accompanying editorial in the journal.

"If these results hold true, further research may help us understand what trait is being passed from parent to child," she added. "Assessing the presence or absence of all potential risk factors for breech presentation, including the parents' own birth positions, may alert the clinician and patient to prepare for a possible breech delivery."

More information

For more on breech births, visit the American Academy of Family Physicians.