Dizano News – The study of 125 women is the first to calculate gestation by pinpointing the exact time of conception.
It found age, time to implantation and their own weight as babies were also linked to pregnancy length.
An expert said the findings, in the journal Human Reproduction, challenged whether a “due date” for women was helpful.
Due dates can be calculated from working out 280 days after the start of the woman’s last menstrual period, or more accurately by ultrasound.
This is the first study to look at pregnancy this way
Yet only 4% of women deliver when predicted and only 70% within 10 days of their estimated due date.
Researchers ‘surprised’
The research team at the US National Institute of Environmental Health Sciences measured hormone concentrations in daily urine samples taken from women trying to conceive naturally to determine exactly when ovulation and implantation of the fertilised egg had occurred.
They found that the average length from ovulation to birth was 268 days, just over 38 weeks.
Once they had excluded six premature births, they found that gestation varied naturally by as much as 37 days.
Dr Anne Marie Jukic said: “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.
Source BCC
Source: Pregnancy length varies naturally by as much as five weeks
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