Length of Healthy Pregnancy Could Vary by as Much as 5 Weeks

A recent study reveals that the length of pregnancy for women can actually vary quite a bit. Researchers looked at the length of 125 pregnancies in order to determine the point where ovulation began and the fertilized embryo became implanted in the womb.

"We found that the average time from ovulation to birth was 268 days - 38 weeks and two days. "However, even after we had excluded six pre-term births, we found that the length of the pregnancies varied by as much as 37 days," said Dr Anne Marie Jukic,  at the National Institute of Environmental Health Sciences (Durham, USA), part of the National Institutes for Health.

"We were a bit surprised by this finding. We know that length of gestation varies among women, but some part of that variation has always been attributed to errors in the assignment of gestational age. Our measure of length of gestation does not include these sources of error, and yet there is still five weeks of variability. It's fascinating," Jukic said, via a press release.

The study was based on data that was collected from the North Carolina Early Pregnancy Study, which focuses on data collected between 1982 and 1985. The study also followed 130 natural pregnancies from conception up until birth, and all of the women who participated in the study were required to provide daily urine samples and maintained a journal regarding their lifestyle.

Researchers also examined the presence of three hormones found in the urine samples-hCG (human chorionic gonadotropin), estrone-3-glucoronide and pregnanediol-3-glucoronide, all of which are connected with the beginning of human pregnancy.

Overall, researchers determined that embryos took longer to implant and also followed a longer gestation period from implantation to delivery. They also found that women who showed late rise in progesterone levels typically had shorter pregnancy--around 12 days short when compared to a typical pregnancy.

More information regarding the study can be found in the journal Human Reproduction.