C-sections interferring with evolution

[herethereandeverywhere]

BBC news link

Essentially: babies being delivered by CS perpetuate the genes that make for a pelvis too narrow to birth a baby naturally. 100 years ago mother and baby would have died and that would have promoted smaller babies/larger pelvises as a natural evolutionary step.

I wonder what the information from this study does to the WHOs stance, and NHS policy on setting an 'ideal' rate of CS.

It's not just pelvic size / baby size mis match that means women have CSs.

Thank you Bonzo I was aware of that. Do you have a view on what the information from this study does to the WHOs stance, and NHS policy on setting an 'ideal' rate of CS?

Not everyone has a C-section because of pelvis size. Mine was because DD was going into distress and I wasn't dilated enough to push. This is true of most of the people I know who had sections. There would just be a much higher infant mortality rate from long labours!

Erm, but if that is the case, how come over all the millenia before CS came in to successful use, humans didnt lose their small pelvises entirely? I mean the article says that babies are getting larger and that's fair enough but before babies started getting larger, mothers and babies were still dying because babies got stuck so the lack of c sections then clearly wasn't de-selecting small pelvises very well.

My pelvis was the right size, my dd wasn't too big, but after over 20 hours of labour, as an older mother, an EMCS was recommended so we didn't both die.

I too wonder what the 'idea' outcome is then. Fewer babies/women surviving? Higher rates of medical intervention going forward? Not sure there is an answer to this quandary.

In one generation on my maternal side we've gone from 5lb babies (mum & siblings, me) to 9lb babies (ds). I defy anyone's pelvis to keep up with that!

Also the percentage increase is very small in the last 50 years and I don't think evolution happens that fast to be honest.

Also, I hope this information does nothing to the WHO/NHS policies on CSs. What is the point of modern medicine if we cant save people's lives? After all, evolutionarily, we are probably weakening humanity by curing many childhood illnesses. If people with genes pre disposing them to certain things survive to have their own children rather than die in childhood, their genes will be passed on so the disease may continue rather than eventually die out. I would still rather medicine cured those children rather than leaving things to evolution and natural selection.

Even if they are correct (which is not certain)...

In evolutionary terms there would be less inherited short--sightedness ( I for one would never have made it to puberty without glasses, if have been eaten by something or fallen down a hole).

And what about all manner of inherited diseases and conditions? What impact is IVF having?

CS seems a very arbitrary one to focus one IMO.

DEMum I don't think you can argue with the evidence. I imagine that over the millenia that you refer to, babies were smaller due to poorer nutrition and gnerally harder lives. There was perhaps a move to reduction though not eradication of smaller pelvises.

I think the culture of trying to keep CS minimised and that 'your body won't produce a baby that you can't deliver' and 'listen to your body it knows what to do' 'relax and refuse intervention, it's what your body was designed to do' is wrong. It's a falsehood. The fact is birth is not easy or safe for many women unless they have severe intervention (CS or forceps). We are setting women up to fail and feel like failures.

There is precious little science/research available on the subject (which is why midwives still recommend old wives tales rather then evidence-based solutions).

I initially read this article and was a bit at the message it appeared to deliver, I.e. That more women and babies should be dying in childbirth rather than medicine intervening. But re-reading it I think it's actually just written from a scientific/clinical stance, and making reference to the fact that 100 years ago significant numbers of women and babies died in childbirth due to complications which could not be medically resolved. I don't think there's any suggestion that anything needs to be done iyswim.

But when you look at it from a clinical perspective, 100 years ago the infant mortality rate was much higher than it is now, which looking back could be considered as natural selection, much like happens within the animal population for instance. To add to that though, women also had signifficantly larger families back then due to a multitude of reasons such as high infant mortality rate but also due to the unavailability of contraception. So while now the natural selection process has been curtailed by the advances in medical science, be that to deliver a baby by different means or to treat conditions which 100 years ago would have resulted in death, the fact that the same medical advances have also produced reasonably effective contraception means that women aren't having such large families any more anyway so the natural selection process doesn't apply any more iyswim.

Written down it looks crass, but from a scientific/clinical perspective it's just a natural fact. So for example many animals will have one baby every year because a large number of them will never make it to adulthood, as such they have to reproduce often in order to preserve the species. But with people that preservation has happened on a more scientific level rather than having to go through the mortality rate and therefore having to have larger families.

Look how high maternal and infant mortality is right now in other parts of the world that don't have our medical care. Should we aim to be roughly the same in order for things to be more natural? Maybe we can scrap all healthcare that doesn't involve chewing some leaves as I'd imagine all modern medicine impacts on natural selection in some way.

Reading the article again, I am a bit confused. They say that the trend towards smaller babies has vanished due to C-sections. But surely the reason we are having larger babies these days (at least in developed countries) is due to better maternal nutrition and medicine and knowing what to avoid - eg. smoking. Evolution/natural selection works at a relative snail's pace compared with the speed of the improvements in nutrition we have seen in recent years. Surely, there is no way our pelvises can keep up with these changes so the increase in CSs seen in only the 50 years referred to in the article is more likely to be down to bigger babies due to better health rather than the fact that increases in numbers of CSs are causing a reverse in smaller babies?

Maybe I am missing something, or maybe it is just that the article isn't fully setting out the reasons behind the conclusion being presented, but I don't think it makes sense.

Well, yes. But innumerable aspects of modern life interfere with evolution and natural selection. I think if they're going to discuss any one in that context it should be any infertility treatment that goes beyond a friend and a turkey baster. Shift infertility to be an issue for counselling, same as bereavement; and to back that up there ought to be a cultural shift away from having children as the default life path/norm. The UN's recent expansion of the concept of infertility to include people who just haven't found a partner doesn't help either. Posted in full knowlege of possible flaming, and that this is not quite the appropriate forum for that idea.

The article is phrased in such a way that I think it would be more likely to make health services conclude a rise in caesearan rates is inevitable due to better nutrition, and from a policy viewpoint to make them less stingy about offering them. It doesn't sound as negative about the phenomenon as the first post to me implies it did. However, pulling in the other direction, the NHS budget is in such a state that they seem unlikely to revise targets to become more expensive.

Do you have children pennycarbonara?

I am not sure how scientifically rigorous this study is. Essentially it's a big data mining exercise with a tendentious theory stretched over to fit. It is not clear how much the author of the study understands the intricacies of labour and birth - as PPs have pointed out there are many, many more reasons for a CS than a 'narrow pelvis' (or cephalopelvic disproportion to give its clinical name). It is fiendishly difficult to diagnose accurately because size is only one indication, and because measurements are often inaccurate, and because other factors (not least maternal age) arguably play a bigger role.

I also think a lot of people oversimplify the process of 'evolution' and misunderstand the complexities of genetic inheritance. Most deaths in childbirth are not due to inherited factors and thus do not have a selective function. Evolution is a very, very blunt and approximate process except in cases of responses to extreme natural catastrophe, and I doubt a bit of surgery over a hundred years or so is going to influence millennia of human evolution by much.

The title of this post is misleading and implies a negative bias.

Caesarean births are NOT 'interfering' with evolution they are 'affecting' it, that is NOT the same thing. The article does not use the word interfering once.

Okay suppermummy, that appear to me like minor semantics but you may have a point that I just can't see. Please could you explain why they are so very different?

If there were no c-sections, evolution would continue unhindered. How is that not interfering with the process of evolution?

But evolution is working. It is not hindered. Our environment and the resources available have changed and so have we in response (possibly!). We are adapting to what's available to us now. Could that set us up to fail? Are we becoming like English Bulldogs who have such exaggerated features that they now mostly need intervention? Maybe. It is certainly something for us to be aware of.

herethereandeverywhere

It is not semantics at all, its a very important difference.

There is no such thing as 'unhindered' evolution. Humans have not come along and hindered, disrupted or polluted the evolutionary process. You make it sound like humans are busy bodies interfering with something perfect.

Evolution is the change in species over time, without that change their is no evolution. All species and natural processes change things which is what enables evolution to continue.

If there were no c-sections, evolution would not happen in this area, it would pause. The C-Sections are evolution in action.

Hope that makes sense.

Thanks suppermummy. I understand the concept of evolution already. If genes that promote small pelvises/large baby heads would have eventually died out without surgical intervention to save the lives of the mother and baby; how is that not interferring with the evolutionary process?

I can understand Forkyou's point that we are still evolving, just perhaps evolving towards many, then most, then all women needing surgical intervention to give birth.

I have said the same about ivf, particularly where lack of conception is due to the father's low sperm count. Will they pass that on to their sons and so the cycle continues?

herethereandeverywhere, You say you understand evolution then go on to explain that you don't understand it. Their isn't an evolutionary process trying to kill off small pelvises/large baby heads which the intervention of C-Sections is stopping from happening.

Would you equally say genes that promote large pelvises/small baby heads to stop deaths in child birth is interfering in the evolutionary process? No, because there is no predetermined goal which can be interfered with.

There are millions of factors that contribute to how we evolve. C-sections and dying in childbirth are 2 of many that all combine to create the outcome. One is not interfering with the other. Unless of course you are taking a religious view that their is some supernatural plan that modern medical intervention is interfering in.

Meh. Modern medicine has effectively offset evolution IMO. There are a great many people alive today who would not have survived to reproductive age in the first place without modern medicine, and so genes associated with pathological biological outcomes get passed on. If you're going to make a fuss about C-sections then surely you have to also make a fuss about all the conditions that modern medicine has treated and continues to treat.

You could say this about SO many things. Flu jabs, infertility treatment, neo-natal care, antibiotics. These things are all 'intefering' with the natural order of things and therefore may or may not have an effect on evolution. Modern life in general probably inteferes with evolution so this is just an example of many.