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