Is there a point in gestation where it becomes medically necessary to induce?

I was born 3 weeks late back in 1981. Nowadays, it seems that doctors don’t let women get a week past their due date before inducing labor. Barring fetal distress, is there a certain point where labor MUST be induced, or will the baby just pop out eventually? What are the consequences if a baby percolates too long?

Wikipedia says the doctors would like you to give birth by 42 weeks into the pregnancy–my completely WAG is that if the baby doesn’t get delivered it would grow too big and cause (possibly fatal) stress on the mother.

It’s possible for the baby to be too big for passage through the woman’s pelvis. The technical term is cephalopelvic disproportion. Of course the baby doesn’t have to be overdue for that to happen but the longer baby is growing inside the more you think about it. One OB I worked with would have her past due patients get ultrasounds every couple of days to monitor the size of the baby. You also worry about meconium aspiration syndrome. Meconium is the baby’s first stool and passage of the meconium into the amniotic fluid is more common with postdate births. But there’s no hard and fast cut-off that I know of where a woman must be induced. The due date isn’t really that precise. Anything between 38 and 42 weeks is considered normal gestation.

Humans already have a harder time in labor due to the conformation of the hips (for walking upright) and the large size of the skull (to allow room for a bigger brain).

So presumably, at some point the baby’s skull would grow too large to fit through the birth canal, so normal birth would be impossible. (Though C-section birth might still work.) I would imagine doctors would induce birth before this point.

Could it be that we have better technology today to establish a more accurate due date?

I can’t really say when it becomes medically necessary to induce labor, but in a book a recently read “Anomalies and Curiosities of Medicine” by George Gould and Walter Pyle

They have cited many cases of “long pregnancies” among them are cases as long as 12 months’ gestation, at which point a cesarien section was necesarry.

And as Ruby says, technology probably aids us in not going too far from the due date, the book was written in 1896, so therefore all of those cases were from the mid-19th century and farther back.

At 42 weeks it becomes safer to induce than not to induce.
After 42 weeks the incidence of intrauterine foetal death is pretty high.
Babies need the placenta to provide oxygen and nutrients, the placenta isn’t designed to work well indefinitely, and by 42 weeks it is generally on its last legs.

So I guess a follow-up question might be - is it possible for a baby to be in the womb that long and still not be developed enough?

Not in the absence of other serious complications. While there is a range in weight, normal babies are functionally fully developed much earlier and are viable babies much earlier along.

We were still being told of the 38 to 42 week window. Ultrasound still doesn’t tell the day or the hour.

I think that phrasing presumes that labor will start when the baby is fully developed. AFAIK, the exact mechanism by which labor is kicked into gear spontaneously is poorly understood. Not for lack of trying, either, as a better understanding of nature’s way of making labor happen could result in more effective artificial inductions when necessary.

Babies are considered “full term” and therefore developed enough by 38 weeks. After that, baby is mostly just putting on weight, which isn’t totally a bad thing as it helps with thermoregulation once baby is out.

The degree of development follows a pretty tight curve, which is why medical professionals can use the developmental milestones to estimate a baby’s gestation when the mother is not sure of dates. This was the case when friends of ours adopted a baby from a woman who wasn’t aware she was pregnant until she showed up at the emergency room with a stomach complaint. Doctors estimated the babe at 36 weeks based on physical atributes.

My wife’s first was not born until 10.5 months, which was very accurately determined and documented. The fetus had been shrinking for a short while, and when born his fingernails were thoroughly grown into the palms of his hands. Her first obstetrician had retired and there was some delay in getting records into the hands of the second, which was part of the reason for waiting so long. She was scheduled for an induction and broke her water the night before while watching Laugh In.

So if the baby is sufficiently developed at 38 weeks, why don’t they normally induce labor at that point, before the baby grows any larger?

Two immediate reasons: an induced labor hurts more and is more prone to requiring further interventions (including c-section) than a naturally occurring labor, and the extra weight a fetus puts on in those last few weeks help him to keep himself warm once he’s born. Most babies, no matter when they’re born, lose about 10% of their body weight the first week of life; if they’re plump, this isn’t a big deal at all, but if they’re low weight, it can get a little scary. If your baby needs any sort of medical treatment, surgery, whatever, you want him to be as robust as possible, and that includes having a little extra meat on his bones.

How many of those “long pregnancies” involved widows who’s husbands had been dead more than a year? :dubious: Or women who’s husbands were at sea or off to war?

Reminds me of a MAS*H episode. A guy is distraught and Hawkeye and BJ are trying to find out why (ISTR he was in the chapel going to take his life or something) and he tells them “I received a letter from my wife today. She’s pregnant” “that’s great! What’s the problem?” “I’ve been over here a year!” (not played for laughs, btw)

There are a few cases cited where that is the case, but Gould and Pyle also cite cases in which the woman has been bedridden or just plain gone way past the due date.

One case that they cite stands out “Tidd relates the case of a woman in Clifton, W. Va expecting confinement on June 1st, going over until September 15th, the fetus being in the uterus twelve months, and nine months after quickening was felt.”

When I worked in labor and delivery, I remember post-mature babies as being skinny with wrinkled skin from loss of subcutaneous fat. The placentas were usually pock-marked with obvious infarcts which increased with the amount of post-maturity.
I avoided any such problem by inducing my second and third at 38 weeks (I was just tired). Because my family has large babies (8.5-10 lbs.), my doc was more than happy to accomodate my whims. They would never do it so readily with a first time mother with an unproven pelvis and unknown baby size.

My mother was born in 1948 just shy of 45 weeks by c-section (and 12 lbs). My grandmother showed no signs labor might happen any time in the near future. She was told that sometimes labor doesn’t start, eventually the baby would die, and then either that would kick off labor or she’d die too.

Prior to the advent of routine C-sections you get occasional references to cases where the baby dies in the womb during labour and isn’t delivered. The mother thus finds herself permanently pregnent.
For example, Pierre Boaistuau’s Histoiries Prodigieuses of 1560 claims that one woman carried such a dead baby within her for five years. Despite the immense risk, she begged to be operated on and the corpse was eventually removed. She not only survived, but went on to successfully bear other children.

Of course, whether such stories are to be believed is another matter. Their readership was meant to be utterly astonished.