Most pregnant women worry about their due dates. You hear it all the time: ‘I am overdue’ or ‘My baby was born early’. But a new study by the US National Institute of Environmental Health Sciences looks at pregnancy length from a whole new perspective. It seems that it can vary by up to five weeks naturally. This could mean that the whole medical perspective on due dates could be flawed.
Pregnancy length revised
The general knowledge is that human gestation has a pretty fixed time frame. Now, the study revealed that pregnancy length could vary by up to 37 days. That is more than a one month variation. Previously, errors in calculating a woman’s due date was attributed to error. But now, the researchers excluded such errors and were surprised by the findings.
The average length of a pregnancy is still over 38 weeks. However, the mechanism that leads to labour is still unknown. So a baby could be born within a much larger time frame than previously thought. At the moment, only 4% of women deliver at their due date.
Why does pregnancy length vary?
The study found there are a few factors that can influence the duration of pregnancy. These are not usually taken under account by gynaecologists. A due date is calculated from the last period and based on ultrasound measurements.
- It takes longer for some embryos to implant. That means that the pregnancy length could be extended over the 42 weeks mark.
- The mother’s weight at birth could also be a factor.
- Another factor is age. It seems that older women have longer pregnancies.
- The length of a previous pregnancy can also be an indication. Women tend to have similar pregnancy lengths.
Intervention during long pregnancies could change
Researchers think that the way doctors intervene in longer pregnancies should change. The idea of a fixed due date should also change. Pregnant women are given a due date that makes them really anxious. Also, gynaecologists are instructed to induce labour in women that are overdue. But the whole meaning of overdue could be flawed.
Unless there is a health problem, doctors should not intervene just because a woman is past her due date. Being overdue needs to be redefined. Right now, many induced pregnancies end up in emergency C-sections or lead to other complications. And a lot of women give birth to healthy babies even after 42 weeks.
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