New research has found that the length of pregnancy can actually vary naturally by as much as five weeks! The surprising findings, in the journal Human Reproduction, have challenged whether a “due date” for women is actually helpful? A study of 125 women calculated gestation by pinpointing the exact time of conception. It was found that the time to implantation, the women’s weight as babies as well as their age were all linked to pregnancy length.
Due dates are calculated from working out when 280 days from the start of the woman’s last menstrual period is, or more accurately by ultrasound. But it is very unlikely for a woman to deliver on their predicted due date with only 4% of women doing so and only 70% of women giving birth within 10 days of their due date.
The study was able to show that embryos that took longer to implant also took longer from implantation to delivery and that older women were more likely to have longer pregnancies. What else was discovered was a consistency in when women deliver, so the length of a previous or subsequent pregnancy would be related to the length of the one being studied.
It can now be said that natural variability is much greater than was previously thought, and so perhaps this should be kept in mind when clinicians are deciding whether to intervene on a pregnancy. If your due date is approaching and you have any questions for the private birth team our independent midwives are here to speak to you at any time.