The length of a completely normal pregnancy can actually vary by up to five weeks, according to a study of 125 women. The study is the first to calculate gestation using the exact time of conception.
The study found that age, time to implantation, and the mother’s own weight when she was born can also factor in to how long her pregnancy will be.
The findings will likely challenge whether a due date for a pregnancy is actually helpful, reports the BBC. Due dates are usually calculated by working out 280 days from the woman’s last menstrual period.
It can also be determined through ultrasound. However, knowing a healthy pregnancy can vary by up to a month would certainly challenge the ability to give an accurate guess.
According to research, just four percent of women will deliver on their due dates. Only 70 percent will deliver within 10 days of their supposed due date.
Yahoo! News adds that the length of a pregnancy is already known to be variable. However, most of the variation was through to be from errors in determining the baby’s age.
But the new study challenges this. Pregnancies in the study lasted 38 weeks on average from the day of conception to the day the baby was born. That amounts to about 40 to 41 weeks from the woman’s last menstrual period.
However, even when they excluded the data from babies born preterm, the length of a pregnancy ranged from 35 to 40 weeks from the day of conception. Researchers were surprised to see the wide variation. Study researcher Dr. Anne Marie Jukic suggested that a range of due dates should be used instead of a single date estimate.
Even with the five-week variation, the study discovered that length of patients’ previous pregnancies were a strong indication of future gestation periods. Other characteristics, such as longer implantation and a late rise in progesterone could help determine a more accurate date.
Some experts were also critical of the study. For example, Dr. Tomer Singer, a reproductive endocrinologist, asserted that the study doesn’t provide much information that wasn’t known already. he added that doctors already emphasize that few women give birth on their due dates. Singer explained that he usually tells patients they can expect to give birth between 37 and 42 weeks of their last menstrual period.
Are you surprised to learn that pregnancy length can very by up to five weeks?
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