This was originally posted on truebirth.com but has disappeared and due to difficulty finding a copy, I'm reposting it here because it is good information. None of the following content is mine, though I certainly back the sentiments (and I inserted an asterisk for a footnote).
Due Date for VBAC: Not an Expiration Date
By Danell Swim April 27, 2008
Being a woman with a prior cesarean, I’ve become extremely supportive of women who choose a vaginal birth after a cesarean (VBAC) like I did. It seems that my support is often falling on deaf ears, as time and again, women are coerced into repeat cesareans for ridiculous reasons. The latest of which, is women who are pregnant after the due date.
I just read of another woman who is “attempting a VBAC” with her doctor. She’s desperately hoping that she’ll go into labor before her Estimated Due Date (EDD), because if she goes even a day past, the caesarean will be scheduled immediately.
This is happening all too often, as doctors seem to believe that an EDD is actually an expiration date. To back up this ideology, they use ridiculous claims to coerce women to go along with these scheduled c-sections. They say that the stillbirth rate increases after 40 weeks, that the number of successful VBACs is lowered, and that the baby will get too big which will make a vaginal delivery too dangerous. There is no evidence to back up these claims, yet doctors continue to practice according to myth and rumor rather than clear medical information.
Despite evidence to the contrary, doctors are still insisting that women only be allowed to attempt a VBAC if labor occurs before the EDD. And, they sell this policy as an actual attempt is made to give the woman an opportunity to have a VBAC in this manner. But how likely is it that a pregnant woman will go into labor before her due date? For that, we have to look at the information regarding EDDs.
About your Due Date
The first piece to understanding your estimated due date (EDD) is the origins. No doubt when the due date calculators online, plus your doctor’s office and any wheel chart all calculated your due date, you assumed some scientific equation that averages out all births? You’d be wrong.
How would you feel knowing that the man who invented the 40 week pregnancy due date, was born… oh, about 230 years ago.* Other notable events in the year of 1778 were: Captain Cook’s discovery of the Hawaiian Islands, England’s declaration of war on France (again), the Revolutionary war raging on, and Franz Karl Naegele’s birth in Germany.
It is called Naegel’s Rule:
The rule estimates the Expected Date of Delivery (EDD) from the first day of the woman’s Last Menstrual Period (LMP) by adding a year, subtracting three months and adding seven days to that date. This approximates to the average normal human pregnancy which lasts 40 weeks (280 days) from the LMP, or 38 weeks (266 days) from the date of fertilisation. Example, if LMP was 8 May 2007, then +1 year = 8 May 2008, -3 months = 8 February 2008, +7 days = 15 February 2008; whereas precisely 280 days would be 12 February 2008.It is remarkable that in such an archaic time of obstetric knowledge, someone was able to come up with a method of dating gestation that is still used today. The only problem with that is that it’s terribly inaccurate, yet doctors continue to use it as gospel.
A study was published in 1990 that examined the average length of pregnancy for white women. Essentially, they found that if you take the date of the LMP + 1 year - 3 months + 15 days (if the woman has not had a prior vaginal birth). If the woman has had a vaginal birth, you add 10 days instead.
So if I were to have my LMP on May 8th 2007, I’d jump ahead to May 8th 2008, then subtract 3 months to February 8th 2008. If I’d already had one baby vaginally, my EDD would be February 18th 2008. If I’d not had any prior vaginal births, my EDD would be February 23rd.
That’s a far cry from February 15th, as Naegel’s Rule states.
Due Date Theories Previous Vaginal Birth No Previous Vaginal Birth
280 Day Rule February 12th February 12th
Naegel’s Rule February 15th February 15th
Avg White Women February 18th February 23rd
Information is limited as to other ethnicities, but one study in England found that Black and Asian women had a gestation approximately 1 week less than white women. In addition, they found that “preterm” black and Asian infants were less likely to exhibit signs of being preterm, which gives more evidence that those babies are more developed than white babies. In layman’s terms: they’re fully cooked. However, previous deliveries, ethnicity and familial traits are never taken into account when estimating a due date. Which is what makes it so unfair that doctors are treating these estimates as scientific evidence.
What this means for VBAC Moms
Let’s assume that Jane Doe is planning her VBAC. Her doctor supports her, but says that she has to go into labor before her due date. Let’s suppose that Jane is white, and hasn’t had any children vaginally before. Her doctor uses that handy dandy chart to predict her due date as May 7th. But, odds are that she won’t go into labor until May 15th.
Poor Jane, has a doctor that was just humoring her with promises of a VBAC. When in reality, he could have predicted all along that she’d end up with another c-section. After all, these are the doctors, they’re the ones that are supposed to be reading the studies and keeping up to date on things as trivial as average gestation.
The VBAC rate is plummeting in this country to less than 9%. Part of this is due to the malpractice fears, and the (soon to be revised) American College of Obstetricians and Gynecologists recommendations, but it’s also due to so many doctors refusing to treat VBAC women as anything but a ticking time-bomb. And, they know that with threats of shoulder dystocia, uterine rupture and placenta accreta, they can scare these women into repeat cesareans if they don’t meet the impossible deadline of their false estimated due date.
Unfortunately for women who desire a VBAC, there’s little you can do but to keep looking for another care provider. Keep looking until you find one that truly understands how the normal human body functions, and is most concerned with giving the patient the birth that they want and need.
Doctors just don’t seem to understand this. And that’s why they keep amusing themselves by allowing women to attempt a VBAC under these circumstances. It’s disturbing how many of them are insisting that VBAC patients deliver before 40 weeks, and it’s ridiculous that women are allowing them to make those decisions for them.
Because let’s face it: having a VBAC isn’t about proving anything, or becoming a “real woman” as so many would like to believe. Having a VBAC is about making the choice to have a healthier birth, a healthier mom and baby, and a healthier reproductive future. It’s about being able to hold your baby without pain.
That’s worth finding another doctor (or midwife).
Overdue? (more info for calculating your due date)
Wikipedia on Naegele’s Rule
The length of uncomplicated human gestation.
Does gestation vary by ethnic group?
Written by Danell Swim · Filed Under Editorials
article archived here
*The creator of the EDD was actually Harmanni Boerhaave, a botanist who used the Bible to create the due date system (he found evidence in there that human gestation is supposed to be 10 lunar months... and then he did the math wrong). So not only was his method created hundreds of years ago, but it was by a botanist... who messed up the math by 15 whole days. Naegele merely publicized the idea and got the "rule" name after himself.