My wife is going to give birth sometime soon (yay). Anyway, her ‘due date’, based on calculations by the obstetrition, was supposed to be 23 march - 8 days ago. This was worked out using 40 weeks from last menstral period.
Based on our calculations using 266 days from conception we get 27 March. This is supposed to be more accurate. Assume that the date of conception is accurate to ± 3 days (my wife is a scientist and keeps good records ).
Now today is 31 March and the obst. is suggestion inducing birth in 2 days.:eek:
So, tring to find the SD on all this I found a reference to a paper published in 1990 by Mittendorf saying the human gestation period for first-time white women is 273 days, based on a review of records of 17,000 births. It also says that the 266 day figure was thought up in 1812 by some goose that believed pregnancy lasted 10 lunar months, NOT on empirical evidence.* :dubious: This is the calculation that all the doctors seem to use.
So, taking a ± 4 day (90% confidence level) from the new due date of 4 April, induction on 2 April would be too soon.
Why do the obst. use 266 days instead of 273? Are there any other studies?
Why are they so keen to induce, when the due-date estimation is based on a dodgy origin?
What about taking into account a natural distribution about the due date?
Any obstetritions, gyno’s, nurses, mothers with attitude like to shed some light on this important matter?
10 Lunar months is 266 days ? Dont think so (9 more like).
My wifes first due date was worked out according to the menstral period (although 2 dates where put forward (Dec 29 or 31), depending on who you talked to).
The ‘more accurate’ due date was worked out by measuring the size of the babys’ head from the ultrasound scan at 19 weeks.
That gave Dec 21st, which is the one the doctors stick to for the rest of the pregnancy.
As it is, we were told that once you have a due date from the scan, the baby can arrive anything from 2 weeks before to 2 weeks after, and be considered ‘normal term’.
Personally I was under the impression that the due date was good to within a few days either side to a high percentage of probability (like your 90% +or- 4 days) - NOT SO.
2 weeks either side, that’s what we were told by several midwives.
If the baby hadnt arrived by due date + 12 days, they would have induced.
As it turned out, the little bugger went oblique breech in week 36, so she had to have a caesarian as it couldnt be turned back the right way.
A lot of this depends on the local health authority - they all seem to have different rules here.
Babies are born when they are ready. I don’t think that large of a percentage are actually induced. I’ve had three and only the last went all the way to the due date and she was born on the due date. I think I willed them out! By the time it gets here your wife will be ready for it to come no matter how many days it’s been.
david simmonds I told my wife to ask the doctor about the reasoning for using such an outdated method when she sees her again - hopefully she wont have to. I suspect the doc. will just say - “oh thats the way we always do it”.
chalkpit et al Apparently Franz Naegele, who came up with the 266 day rule in 1812, said that the 10 lunar months is from the first day of the mothers last menstrual cycle. I did not want to overload you with facts earlier, but I am glad you display perspicacity.
If one subtracts 14 days from the (29.53059 x 10 lunar months), to take into account then time between period and ovulation, one arrives at 281 days (40 weeks).
The point is - Why Naegele’s calculation still used, when more recent empirical observations are available?
I thought you were referring to the time interval between two lunar cycles, which is (on average, I might add) 29.53059 days.
I was unaware of there being other interpretations of the phrase, and was consequently surprised to see it being used as 28 days. (Especially as the math becomes so much nicer with 29.53059 days/month; it comes ou as (almost) exactly 9 months per 266 days.
But, if that’s the common usage in obstretics, I will yield for the duration of this argument.
This is a subject I’m not (yet) experienced in, so I will now withdraw any smart-ass comments.
ChalkPit: This site just emphasises how varied and WAG the calculations that ‘they’ use are. In this site it said that 28 day and 29.53059 day estimates are both used.
Problem is, if the obst. underestimates of due date by 3 weeks then a medically induced premiturity could occur - Iatrogenic Prematurity. Using these WAG calculations I can see that this would be a not uncommon event.
As far as being premature goes, we were told that anything after week 37 was considered full term.
I cant see how an error in due date of 3 weeks, would go unnoticed throughout the entire term, what with all the checkups which occur throughout the period. Did your wife ever have an ultrasound scan done ?
But then, like I said in my first reply, we were told that 2 weeks either side is the best you can hope for accuracy-wise. Working on 3 or 4 days either side seems a bit optimistic to me, unless your medical people have explained the due date to you in those terms.
I will point out this thread to my wife Cyn when she gets home. Shes a labor and delivery nurse and does inductions all the time.
There are a variety of medical reasons to induce a little early. One of them is Macrosomia (BIG BABY!) if baby is getting so big the OB is fearing her uterus may rupture they will take baby early. If she calls me I will ask her for a “top 5 reasons” or something.
For reference does your wife have any other medical history related to her pregnancy like gestational diabetes, pregnancy induced hypertension, or prior reproductive health issues?
I didn’t mean that the question should be asked in a confrontational way. People seem to be reluctant to ask the doctor to explain things to them. If your best source of information about this particular pregnancy isn’t the doctor handling it then there’s something wrong.
antechnius - I don’t think regardless of how the due date was calculated that there is a true gestation term for humans. Babies come when they are ready, but some babies don’t know how to signal that they are ready, and then you run into worse issues - a woman I work with here refused to be induced initially and ended up well over three weeks overdue. She had to have a C-section and her baby ended up nearly twelve pounds with an infection in her lungs from drinking amniotic fluid filled with her meconium.
Rather than questioning the due date calculation, I would insist upon an ultrasound prior to inducing. They can estimate the baby’s weight via one (I had one a day before my son was born and the estimate was only off by a couple of ounces.) If they say anything over 8 pounds, the odds of prematurity at inducing are extremely small.
Too soon- or not. They should have done a non-stress test by now to make sure that the baby is still doing okay. This is when you lie down for a bit and they monitor how many moves the babby makes in a certain amount of time and what his heart rate does before and after moving.
My first baby was by the due-date calculation due August 28th. I can tell you to within 15 minutes when he was conceived as we only had sex once after my last period and that was it, and my due date (40 weeks) was August 21st.
They did not do a non-stress test on me, and they should have. When they finally induced me on September 4th (exactly one week by their calculations and two by mine) the baby had NO amniotic fluid left. Placental function had started to deteriorate. Because he had no fluids left, he was severely distressed and had voided his bowels. There’s a tar-like substance called meconium that acts as a place-holder to keep the intestines from growing back together. The baby practices swallowing and breathing amniotic fluid, but since there wasn’t any of that left, he breathed in the meconium. Luckily, the umbilical cord which was wrapped three times around his neck kept him from breathing very deeply so it could have been worse.
He was in the neonatal ICU for a week and now he’s an overactive, extremely healthy four-year-old.
I tell you this not to frighten you but to impress upon you how essential regular testing is in late births. If you are certain of your date, then be a pain in the ass about it if you need to. We were lucky. I suspect he had a matter of hours left to live had he not been born when he was. Had I known then, I might have saved us both some agony.
HennaDancer
I forgot to say that my first son was born 9 pounds 10 ounces- and they said due to the fluids not going back in him due to the cord being around his neck, he should have been 10 pounds 4 ounces.
My mother just has big babies (the youngest was a runt at 9 pounds) and so I thought I would, too, and I was expecting that starting at 10 pounds, the second one would be 11 or 12. he was 8 pounds 8 ounces- which only reinforces my claim that the first one was overcooked.
Incidentally, just in case she’s freaking out about now (I was!) I did that huge first baby with no tearing at all. It’s hard if you’re an American woman not to fight your body, but if you can relax and let the animal body take over during labor- push ONLY when your body tells you to- then things will go pretty smoothly most of the time.
HennaDancer
The best due date calculations take into account the length of the average mentrual cycle. Mine is 34 not 28 and that adds several days to the pregnancy. That gave me the due date of May 1 which oddly enough matched my ultrasounds. I was glad that it was later than the due date that took LMP alone into account. I want to avoid induction. At this point my doc is doing weekly non-stress tests though, just to make sure.
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