As reported by Parents, June 1, 2004.

Past Due?

Carrying a girl may mean a prolonged pregnancy, new research shows.

By Beth Turner

June 1, 2004 — For some moms-to-be, their due date can't come soon enough. Yet when it passes -- and still no baby -- it can be frustrating. However, new studies show that the sex of the baby and its time in the womb may be linked.

Contrary to previous reports that carrying a boy means a longer pregnancy, it appears now that girls are more likely to be delivered past their due date, according to new research from the University of Connecticut Health Center.

Researchers investigated the association between fetal gender and postdate delivery in the U.S. population from 1990 to 2001. Using data from the National Center for Health Statistics, the researchers examined births of single babies, twins, and triplets. In each of the categories, males were associated with preterm delivery and females were associated with prolonged pregnancy.

"This [prolonged pregnancy with females] holds across the board -- for singletons, twins, and triplets," says Dr. James Egan, one of the researchers. "And it becomes a bit more pronounced as you move up in higher order of multiple triplets."

There are many reasons why this correlation might be possible, Dr. Egan suggests, including that it might be related to female hormones, or even to size, since male babies generally tend to be a little bigger than female babies. But whatever the reason, Dr. Egan warns this research is not to be thought of as a definitive rule.

"This is not a way of predicting that if you identify a female gender in a fetus, you're more likely to have a prolonged pregnancy. It's not that precise. But if you look at [deliveries] on a population basis, males are a bit more likely to deliver early," Dr. Egan says.

If you have any concerns about your due date, baby-to-be, or any other pregnancy-related question, you should speak to your doctor.