Counting the Days Until the Baby Comes, Whats the Due Date

Move that pin in the calendar back two weeks. Full term in pregnancy is no longer "37 to 40 weeks" it's 39 weeks. Patients are dismayed to find out that elective inductions and elective C-sections (other than medically indicated) that are scheduled at full term, mean, full term. So if you have a due date, think of that as when you are due. Complex? No, but times are hard to change.

We hat changing names, for instance why are we still calling the due date EDC an EDD?? Estimated Date of "Confinement" an "Estimated Date of Delivery" That both incorrect, a bit threatening, and quaint abbreviation has just not gotten out of our lingo! Traditionally we gynos talk in lunar months: ten. To get the ten lunar months we talk about 280 days after the LMP (last menstrual period). And of course that approximates an exact 14 days of non-pregnant pre-ovulatory days. So the actual length of pregnancy is estimated to be 266 days. In my 1903 first Williams Obstetrics he quotes Ahfeld's classic study of length of pregnancy based on women who's due date was known by their exact date of sex. He calculated 269.9 days. And of course even at the turn of the last century we knew pregnancy could be prolonged by rest.

And for most women it's interest in when that clock exactly started to tick. For women with no periods, say a breast feeding women lack of period sign isn't even there. So there was the tried and true: my abdomen is expanding, or the even less reliable, "my baby doesn't like the taste of my breast milk any more!" But least you think those Victorians were so behind they even knew techniques to prolong the onset of  labor. Mme Laurie showed that of 1550 women allowed to just rest in the hospital could prolong their pregnancy by as much as 20 days.

Now days it's that first ultrasound for those without regular periods or for those who And then again due dates of those who don't know their sex timing. But the due day became almost a due month when full term started to be thought of as 37 weeks.

I've been surfing my books for when the concept of full term crept in to be 37 weeks, as the old text books all seem to plop that due date at the date. But it was really in the past year that the concept of getting to 39 weeks, rather than assuming babies are as ready at 37 as 39, took hold so firmly that hospital policies make you not get an elective induction unless you are the full 39 weeks. And it has to do with the baby being ready. And a healthy baby is ready, just as the clock hits that actual day.


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