NationStates Jolt Archive


Pregancy a struggle between mother and foetus?

Eutrusca
14-03-2006, 16:33
COMMENTARY: An interesting take on some of the consequences to both mother and child of the struggle between the two during pregnancy. An ob-gyn doctor once told my wife that a foetus is "like a little parasite," and that the baby would get what it needed even if it meant that the mother had to suffer for it. But it now appears that the process is far more complicated than that.


Silent Struggle: A New Theory of Pregnancy (http://www.nytimes.com/2006/03/14/health/14preg.html?th&emc=th)


By CARL ZIMMER
Published: March 14, 2006
Pregnancy can be the most wonderful experience life has to offer. But it can also be dangerous. Around the world, an estimated 529,000 women a year die during pregnancy or childbirth. Ten million suffer injuries, infection or disability.

To David Haig, an evolutionary biologist at Harvard, these grim statistics raise a profound puzzle about pregnancy.

"Pregnancy is absolutely central to reproduction, and yet pregnancy doesn't seem to work very well," he said. "If you think about the heart or the kidney, they're wonderful bits of engineering that work day in and day out for years and years. But pregnancy is associated with all sorts of medical problems. What's the difference?"

The difference is that the heart and the kidney belong to a single individual, while pregnancy is a two-person operation. And this operation does not run in perfect harmony. Instead, Dr. Haig argues, a mother and her unborn child engage in an unconscious struggle over the nutrients she will provide it.

Dr. Haig's theory has been gaining support in recent years, as scientists examine the various ways pregnancy can go wrong.

His theory also explains a baffling feature of developing fetuses: the copies of some genes are shut down, depending on which parent they come from. Dr. Haig has also argued that the same evolutionary conflicts can linger on after birth and even influence the adult brain. New research has offered support to this idea as well. By understanding these hidden struggles, scientists may be able to better understand psychological disorders like depression and autism.

As a biologist fresh out of graduate school in the late 1980's, Dr. Haig decided to look at pregnancy from an evolutionary point of view. As his guide, he used the work of Robert Trivers, an evolutionary biologist at Rutgers University.

In the 1970's, Dr. Trivers argued that families create an evolutionary conflict. Natural selection should favor parents who can successfully raise the most offspring. For that strategy to work, they can't put too many resources into any one child. But the child's chances for reproductive success will increase as its care and feeding increase. Theoretically, Dr. Trivers argued, natural selection could favor genes that help children get more resources from their parents than the parents want to give.

As Dr. Haig considered the case of pregnancy, it seemed like the perfect arena for this sort of conflict. A child develops in intimate contact with its mother. Its development in the womb is crucial to its long-term health. So it was plausible that nature would favor genes that allowed fetuses to draw more resources from their mothers.

A fetus does not sit passively in its mother's womb and wait to be fed. Its placenta aggressively sprouts blood vessels that invade its mother's tissues to extract nutrients.

Meanwhile, Dr. Haig argued, natural selection should favor mothers who could restrain these incursions, and manage to have several surviving offspring carrying on their genes. He envisioned pregnancy as a tug of war. Each side pulls hard, and yet a flag tied to the middle of the rope barely moves.

"We tend to think of genes as parts of a machine working together," Dr. Haig said. "But in the realm of genetic conflict, the cooperation breaks down."

In a 1993 paper, Dr. Haig first predicted that many complications of pregnancy would turn out to be produced by this conflict. One of the most common complications is pre-eclampsia, in which women experience dangerously high blood pressure late in pregnancy. For decades scientists have puzzled over pre-eclampsia, which occurs in about 6 percent of pregnancies.

Dr. Haig proposed that pre-eclampsia was just an extreme form of a strategy used by all fetuses. The fetuses somehow raised the blood pressure of their mothers so as to drive more blood into the relatively low-pressure placenta. Dr. Haig suggested that pre-eclampsia would be associated with some substance that fetuses injected into their mothers' bloodstreams. Pre-eclampsia happened when fetuses injected too much of the stuff, perhaps if they were having trouble getting enough nourishment.

In the past few years, Ananth Karumanchi of Harvard Medical School and his colleagues have gathered evidence that suggests Dr. Haig was right. They have found that women with pre-eclampsia had unusually high levels of a protein called soluble fms-like tyrosine kinase 1, or sFlt1 for short.

Other labs have replicated their results. Dr. Karumanchi's group has done additional work that indicates that this protein interferes with the mother's ability to repair minor damage to her blood vessels. As that damage builds up, so does her blood pressure. And as Dr. Haig predicted, the protein is produced by the fetus, not the mother.

"When I first came across David Haig's hypothesis, it was absolutely cool," said Dr. Karumanchi. "And it made me feel like I might be on the right track."

[ This article is two pages long. Read the rest of the article here (http://www.nytimes.com/2006/03/14/health/14preg.html?th&emc=th). ]
Keruvalia
14-03-2006, 16:34
I knew it! Fetuses are a menace to society and must be wiped from our planet to ensure our glorious future.

Kill a fetus for Jesus today!
Lunatic Goofballs
14-03-2006, 16:38
Spoiled little brats! :D
Jello Biafra
14-03-2006, 16:39
Wow. Fascinating, and yet creepy.
Ilie
14-03-2006, 16:50
It's true. It's the same for after the baby is born: we tell our clients that they have to eat very nutritiously while breastfeeding...not so as to give their babies the best breastmilk possible, but to keep themselves alive and well.

Through breastmilk, babies extract the exact amount of each nutrient it needs from the mother's body, so breastmilk is always perfectly nourishing. Breastfed babies are perfectly nourished even in famine conditions.

That means that if the mom doesn't eat food containing the same stuff the infant takes from her, the nutrients will be extracted from her to the detriment of her own health.
Lunatic Goofballs
14-03-2006, 16:54
It's true. It's the same for after the baby is born: we tell our clients that they have to eat very nutritiously while breastfeeding...not so as to give their babies the best breastmilk possible, but to keep themselves alive and well.

Through breastmilk, babies extract the exact amount of each nutrient it needs from the mother's body, so breastmilk is always perfectly nourishing. Breastfed babies are perfectly nourished even in famine conditions.

That means that if the mom doesn't eat food containing the same stuff the infant takes from her, the nutrients will be extracted from her to the detriment of her own health.

So it's kind of like paying taxes.
Sinuhue
14-03-2006, 16:54
It's true. It's the same for after the baby is born: we tell our clients that they have to eat very nutritiously while breastfeeding...not so as to give their babies the best breastmilk possible, but to keep themselves alive and well.

Through breastmilk, babies extract the exact amount of each nutrient it needs from the mother's body, so breastmilk is always perfectly nourishing. Breastfed babies are perfectly nourished even in famine conditions.

That means that if the mom doesn't eat food containing the same stuff the infant takes from her, the nutrients will be extracted from her to the detriment of her own health.
I was told that too, and it is certainly true. Don't drink enough water, and you get dehydrated while nursing at a much faster rate. Duh! If you don't have a steady intake of vitamins, such as calcium, the baby will get it from your stores...possibly weakening your bones. You can't stop it, or turn it off. If you aren't eating well, the baby will suffer less than you do, because again, your body will provide the nutrients to the best of its ability, regardless of how that affects you.

Good health during pregnancy, and nursing, is vital for both the baby and the mother...but the baby has an advantage in some ways.
Smunkeeville
14-03-2006, 16:55
I remember a mothers day sermon at church when my oldest was almost 1, the preacher speaking to children said "from the moment you were concieved you started pushing and kicking and taking what you needed, you took things that your mom needed to make yourself better, you made her body work for you, when you were born you made her work for you, she woke up on your command, changed you when you wanted, cuddled you when you needed it, your whole life your mother has been in service to you.....so today fix her a sandwich you spoiled brat!"

everyone laughed, except for a small kid sitting in my pew who started crying he told his mom "I didn't know I was so mean, I'm sorry"

the preacher felt so bad.
Eutrusca
14-03-2006, 17:10
I knew it! Fetuses are a menace to society and must be wiped from our planet to ensure our glorious future.

Kill a fetus for Jesus today!
** SLAP **
Psychotic Mongooses
14-03-2006, 17:11
** SLAP **

With, or without the fish?
Eutrusca
14-03-2006, 17:12
It's true. It's the same for after the baby is born: we tell our clients that they have to eat very nutritiously while breastfeeding...not so as to give their babies the best breastmilk possible, but to keep themselves alive and well.

Through breastmilk, babies extract the exact amount of each nutrient it needs from the mother's body, so breastmilk is always perfectly nourishing. Breastfed babies are perfectly nourished even in famine conditions.

That means that if the mom doesn't eat food containing the same stuff the infant takes from her, the nutrients will be extracted from her to the detriment of her own health.
My wife had two of our children while I was still in the military. The military doctors seemed to have a much better grip on this issue long before most civilian doctors. I have never seen so many dieatary supplements issued by doctors either before or since! :)
Eutrusca
14-03-2006, 17:13
With, or without the fish?
Sorry about that. I didn't have time to find the damned trout. He needed slapping right away! :D
Psychotic Mongooses
14-03-2006, 17:15
Sorry about that. I didn't have time to find the damned trout. He needed slapping right away! :D

Odd the way a simple trout can symbolise so much.... :D
Eutrusca
14-03-2006, 17:15
I was told that too, and it is certainly true. Don't drink enough water, and you get dehydrated while nursing at a much faster rate. Duh! If you don't have a steady intake of vitamins, such as calcium, the baby will get it from your stores...possibly weakening your bones. You can't stop it, or turn it off. If you aren't eating well, the baby will suffer less than you do, because again, your body will provide the nutrients to the best of its ability, regardless of how that affects you.

Good health during pregnancy, and nursing, is vital for both the baby and the mother...but the baby has an advantage in some ways.
Perzactly.

It was only recently that researchers concluded that this was one reason for early osteoporosis in women who breast fed their babies.
Eutrusca
14-03-2006, 17:16
Odd the way a simple trout can symbolise so much.... :D
You think that's odd? Do you know Czardas? :D
Eutrusca
14-03-2006, 17:16
I remember a mothers day sermon at church when my oldest was almost 1, the preacher speaking to children said "from the moment you were concieved you started pushing and kicking and taking what you needed, you took things that your mom needed to make yourself better, you made her body work for you, when you were born you made her work for you, she woke up on your command, changed you when you wanted, cuddled you when you needed it, your whole life your mother has been in service to you.....so today fix her a sandwich you spoiled brat!"

everyone laughed, except for a small kid sitting in my pew who started crying he told his mom "I didn't know I was so mean, I'm sorry"

the preacher felt so bad.
Awww! Bright kid! :D
Whereyouthinkyougoing
14-03-2006, 17:17
everyone laughed, except for a small kid sitting in my pew who started crying he told his mom "I didn't know I was so mean, I'm sorry"
Aw.

Thanks for that article, Eutrusca (your posts keep reminding me to read the Times more regularly again), really interesting.

Esp. the genetics part: Only a few of these genes have been carefully studied to understand how they work. But the evidence so far is consistent with Dr. Haig's theory. One of the most striking examples is a gene called insulin growth factor 2 (Igf2). Produced only in fetal cells, it stimulates rapid growth. Normally, only the father's copy is active. To understand the gene's function, scientists disabled the father's copy in the placenta of fetal mice. The mice were born weighing 40 percent below average. Perhaps the mother's copy of Igf2 is silent because turning it off helps slow the growth of a fetus.

On the other hand, mice carry another gene called Igf2r that interferes with the growth-spurring activity of Igf2. This may be another maternal defense gene. In the case of Igf2r, it is the father's gene that is silent, perhaps as a way for fathers to speed up the growth of their offspring. If the mother's copy of this second gene is disabled, mouse pups are born 125 percent heavier than average.
I haven't got my head wrapped around this yet. E.g. who decides whose gene will be turned off?
Does the fetus itself somehow make sure that the respective genes are turned off? That doesn't make sense, seeing how the fetus would surely prefer to have them both turned on (or off, depending on what the genes do) in order to maximize its own profit. (Egads, a capitalist in the making! :eek:).
So is it decided via genetic commands that come inbuilt in the mother's and father's genes? Because then it would be a struggle between the parents rather than between mother and child, wouldn't it?
Jello Biafra
14-03-2006, 17:19
Because then it would be a struggle between the parents rather than between mother and child, wouldn't it?I got the impression that it was the mother who shut the genes off, but I could be mistaken.
Eutrusca
14-03-2006, 17:24
Thanks for that article, Eutrusca (your posts keep reminding me to read the Times more regularly again), really interesting.

Esp. the genetics part:
I haven't got my head wrapped around this yet. E.g. who decides whose gene will be turned off?
Does the fetus itself somehow make sure that the respective genes are turned off? That doesn't make sense, seeing how the fetus would surely prefer to have them both turned on (or off, depending on what the genes do) in order to maximize its own profit. (Egads, a capitalist in the making! :eek:).
So is it decided via genetic commands that come inbuilt in the mother's and father's genes? Because then it would be a struggle between the parents rather than between mother and child, wouldn't it?
You're very welcome. I love this sort of thing ... right out there on the leading edge, it is.

I got the impression that any "settlement" is the result of a sort of ongoing "negotiation" between the foetus and the mother.
Whereyouthinkyougoing
14-03-2006, 17:26
Okay, I'm rereading the article right now, but can I just say real quick how much I love the random "edited by"s popping up all over the place?

Hilarious! :D


Edited (by me!) to add: Yay, I got one too! :p Nice work, Leafanistan.
Eutrusca
14-03-2006, 17:28
Okay, I'm rereading the article right now, but can I just say real quick how much I love the random "edited by"s popping up all over the place?

Hilarious! :D


Edited (by me!) to add: Yay, I got one too! :p Nice work, Leafanistan.
Yeah. I keep getting editied by "Clan Somke Jaguar!" Where is that lil dweeb? I wanna just smack 'im! :D
Whereyouthinkyougoing
14-03-2006, 17:41
JB & Eut: It does sound like the mother is doing the switching off: Dr. Haig also made some predictions about the sorts of maternal defenses that have evolved. One of the most intriguing strategies he proposed was for mothers to shut down some of the genes in their own children.
And with the two gene examples quoted above, that would make sense, I guess: in the first one, she turns her own gene off, to keep fetus growth slow. In the second one, she turns her own gene on, because here "off" would mean more fetus growth.

But I still think it's maybe a bit of both (as in a fight between mother and fetus, and mother and father):
Scientists do not fully understand this process, known as genomic imprinting. They suspect that it is made possible by chemical handles called methyl groups that are attached to units of DNA. Some handles may turn off genes in sperm and egg cells. The genes then remain shut off after a sperm fertilizes an egg.
So, judging from the two examples above (which are only two of 70 such "inactive" genes known today per the article, so who knows if the pattern holds up), the genes in the sperm cells each are active or inactive so as to assure the maximum gain/growth/whatever for the fetus (and, thus, guaranteed survival and spreading of the father's genetic material). The genes in the egg cells, on the other hand, each are active or inactive so as to assure that this gain/growth/whatever can not be maximized.

That does sound more like a struggle between the mother and father to me, albeit one being fought by proxy, i.e. through the fetus.
Muravyets
14-03-2006, 18:18
Fascinating. Thanks, Eutrusca. I saved the article for further study.
Dempublicents1
14-03-2006, 20:01
I remember a mothers day sermon at church when my oldest was almost 1, the preacher speaking to children said "from the moment you were concieved you started pushing and kicking and taking what you needed, you took things that your mom needed to make yourself better, you made her body work for you, when you were born you made her work for you, she woke up on your command, changed you when you wanted, cuddled you when you needed it, your whole life your mother has been in service to you.....so today fix her a sandwich you spoiled brat!"

everyone laughed, except for a small kid sitting in my pew who started crying he told his mom "I didn't know I was so mean, I'm sorry"

the preacher felt so bad.

AAwwwwwwwww! Poor kid!


I got the impression that it was the mother who shut the genes off, but I could be mistaken.

They are talking about fetal genes, so only the fetal cells could possibly actually deactivate them. However, this could be as a response to some factor received from the mother.
Dinaverg
14-03-2006, 21:01
They are talking about fetal genes, so only the fetal cells could possibly actually deactivate them. However, this could be as a response to some factor received from the mother.

Well, where'dya think those fetal cells got the genes from in the first place? :P the genes get mixed up in meiosis anyways...fetal cells don't do much to the genes I think....IIRC imprinting happens with the production of gametes.
Dempublicents1
14-03-2006, 22:16
Well, where'dya think those fetal cells got the genes from in the first place? :P

That's rather irrelevant, since the fetal cells are in control of their own gene expression. If the purpose was to suggest that some genes are altered in the gametes, then that should have been stated.

the genes get mixed up in meiosis anyways...

Indeed, which means that they are even further from actual maternal/paternal genes, or at least can be.

fetal cells don't do much to the genes I think....

You think wrong. Methylation (which can permanently shut off a gene) occurs as do other alterations in the genome - leading to what we call "epigenetic traits." In some cases, only one copy of a gene should be used, and entire copies are shut down. In females, we see a near-entire shutdown of one of the X chromosomes, leading to the appearance of Barr bodies in her cells.

Interestingly enough, these changes are the reason that a clone does not necessarily look just like the animal it was cloned from. If you've seen the pictures of the first cloned cat, her coloring looks nothing like the cat she was cloned from.

IIRC imprinting happens with the production of gametes.

Imprinting does - but all genomic modification is not imprinting. Some genes that are methylated in the gametes (especially in the sperm) are demethylated in the embryonic cells during development and may or may not be remethylated later.