News Release

Father's genes may play a role in timing of birth

Risk of recurrence of prolonged pregnancy, BMJ Volume 326, P 476

Peer-Reviewed Publication

BMJ

A father’s genes may play a role in the timing of birth and in the risk of repeating a prolonged pregnancy, suggest researchers in this week’s BMJ.

Prolonged pregnancy - a pregnancy with a gestational length of 294 days or more - occurs in about 5% of all births. It is associated with a higher incidence of complications in the mother and child, but little is known about it causes.

The team identified all women with a prolonged pregnancy in the first delivery and in a subsequent delivery during 1980-94, and a sample of women with two or more pregnancies recorded in the period 1980-92 (only the first two deliveries were used for analysis).

The post-term group included all women who had a singleton live infant born post-term (42 weeks or more) and a subsequent live infant. The term group included all women who had a singleton live infant born at term (37-41 weeks) and a subsequent live infant. This gave 21,746 sibling pairs in the post-term group and 7,009 sibling pairs in the term group.

The risk of recurrence of post-term delivery was 19.9%. It increased with increasing gestational age to approximately 30% for a gestational age of 44 weeks. In the term group, 7.7% were post-term in the subsequent birth.

However, the risk of recurrence of post-term delivery was reduced to 15.4% when the first and second child had different fathers. Length of pregnancy differed by more than one week in women who had changed partners, compared with those who had not.

We believe that this is a new observation, say the authors. It suggests that the timing of birth may, in part, be determined by paternal genes, they conclude.

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