This article is from the WebMD Medical News Archive

April 9, 2004 -- Babies are born at night, right? Not so: Early afternoon is actually the most common time for child birth, new research shows. Fall is the most common season.

In labor-and-delivery, 1 p.m. to 2 p.m. is prime time, reports researcher Peggy J. Mancuso, PhD, a nursing professor at Texas Women's University. Her paper appears in this month's Obstetrics & Gynecology.

In her study, Mancuso analyzed one year's worth of deliveries at Parkland Hospital in Dallas. Only spontaneous-labor births (not cesarean sections) of one baby -- not multiples -- to women considered low risk for complications.

Mancuso also found:

• Child birth occurred equally on any given day.
• Every hour of the day, a baby was born.
• Fewest births were between 10 a.m. and noon.
• Most births occurred in the fall, between September and November.
• Child births were least common in the winter during the months December through February.
• Women who had given birth before delivered most often between 8 a.m. and 10 a.m.

The mother's age didn't make a difference in delivery time, she says. Daylight Savings Time didn't affect the birth patterns either. It's not clear what influences the time of a birth, but it may be the mother's and baby's hormones, Mancuso writes.

The seasonal patterns in child birth have been observed in other studies, and appear to be related to the weather. In northern Europe, for example, births peak in the spring; fewest births occur in fall and winter months. "In contrast, we found the fewest number of births during the spring, suggesting that women were least likely to conceive during the hottest months," she writes.

Warm weather may affect semen quality -- as was found among outdoor workers in San Antonio, Texas -- which would certainly affect timing of child birth, Mancuso reports. "They found that semen quality decreases in the summer and concluded that this correlated with decreased fertility in the hottest months of the year," she writes.

SOURCE: Mancuso, J. Obstetrics & Gynecology, April 2004; vol 103: pp 853-858.

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