A recent study is creating controversy over the conclusions drawn from the data, explaining a possible effect of caesarean sections. By becoming increasingly caesarean sections since the 50s, many babies have been saved who, if the caesarean section did not exist, would have died in childbirth, and could even have ended the mother's life.
They talk about births in which the baby is big to be born (what is known as cephalopelvic disproportion), in a situation where, when the baby dies, and perhaps also the mother, they would not genetically transfer the problem to their descendants and humans we would evolve towards easier births. It is true? Is caesarean section affecting human evolution by allowing the survival of large babies to be born?
What is being commented about the study
The research, published a few weeks ago, highlights what they are about to consider an "obstetric dilemma", showing that thanks to C-sections, cases of Cephalopelvic disproportion (DCP) They have increased 20 percent since the caesarean section was extended as usual practice in hospitals around the world in the 1950s.
According to the researchers, there are babies who are too big to be able to go through their mother's pelvis, who would normally die at birth, and in some cases it would mean the mother's death as well. This would happen because of the size of the baby (too large), the size of the pelvis (too narrow) or a combination of both situations.
According to the laws of evolution, if women with narrow pelvises do not get enough offspring or even die in childbirth, their line of succession slows down, moving on the line of women most likely to survive: those with a wider pelvis. In addition, babies who are too big, when they die in childbirth, do not live to have large children (due to genetic inheritance), and thus only those who are not large enough to not be able to be born survive. This evolution would mean that, in the future, women had a more or less wide pelvis, and babies not too exaggerated.
But as they explain, thanks to caesarean section, babies survive despite being large, and women with the narrow pelvis also have their babies (and they also survive), so that natural selection does not act and we stop evolving as a species.
In researchers data, as we read in CadenaSer, the cases of DCP have increased from 30 per 1,000 deliveries in the 60s to 36 per 1,000 In the current era.
But how will the species change so much in such a short time?
Well, this is the first thing we all ask ourselves. That since the 50s only 66 years have passed and in such a short time it seems very difficult for such an important variation to be seen in data.
As we read in Newscientist, the evolution of a species can occur in a short time if the environmental changes are drastic enough, and we don't talk about one, but about two or three generations.
However, we are comparing 66 years with hundreds of thousands of years that our species has. In all that time, the line of succession of women with narrow pelvis has become more than extinct, so we are currently living at the time when women have a pelvis quite correct for the size of babies. In addition, environmental change is not so drastic. A global epidemic is a drastic environmental change, a war that will affect the entire species, that will begin to have a shortage of water, or a shortage of sun, or a shortage of food. But Caesarean section cannot explain such a large variation in such a short time.
And the cases of cephalopelvic disproportion increasing?
Although the researchers blame him for the human intervention that affects evolution (these women would have died and their daughters would not now have births with DCP, which increase incidence rates), most likely they are a simple increase in diagnosis: current medicine is not the same as that of six decades ago, so it is now said that there are cases of PCD in women who would not be diagnosed at that time (that's why they have also increased cesarean section rates in all these years).
I want to say with this that I doubt that in only two or three generations the cases have increased by 20% due to a question of offspring, and everything seems to indicate that DCP is being diagnosed more times than it really should be done, especially since it is very rare for a woman to have a pelvis so narrow that she cannot give birth to her own child. In fact, it doesn't make much sense to be able to gestate your baby and then the baby can't be born because it doesn't fit because of her mother's pelvis.
This happens in cases of rickets of the mother (a pelvis that is really small due to vitamin D deficiency in childhood) or in accident cases that will cause some kind of problem in the pelvis. Beyond this, which in our time is unlikely, it is difficult to have a true DCP, if it is not because the woman is the grave to give birth, for example (preventing the sacrum from opening backwards and thus causing that, really, the pelvis may not open enough) or because the woman is in an inappropriate environment to get carried away and dilate and give birth based on her rhythms and needs.
But there are really cases in which the woman cannot give birth to her baby
Sure, and for that there is the caesarean section. But the WHO states that caesarean section should be done at most in 10-15% of deliveries, and yet we are well above.
If you look at this map of Spain, with data from 2011, the difference in caesarean sections is so sharp among autonomous communities, so evident that the difference may not be the size of the woman's pelvis, but other very different factors. Why in the Basque Country do they not reach 13% and in Caesarean areas duplicate in Extremadura? Are the Basque women wider than the hip?
The difference is, above all, in birth care. An attention in which the woman has time, tranquility, a pleasant atmosphere, an adequate support, the appropriate words, affection and professionalism will result in much lower caesarean section rates than an attention in which the woman does not have freedom of movement, she must remain lying next to a monitor and does not feel in a climate of trust because professionals make her feel less capable.
In other words: when women believe in their possibilities, they are able to give birth, on many occasions, to a baby larger than the one who may not be able to give birth in an environment that does not seem conducive to giving birth.
"If it's just giving birth, the baby fits or doesn't fit," many will say. But it's not like that. It is not a matter of physics. We are not talking about a rigid ball that enters or not through a hole that is also rigid. We speak of a soft and malleable baby that must pass through a birth canal that can open more or less according to the posture where the woman is (lying down, sure it opens less) and as the trust Y the environment When everything happens, they are absolutely key in the process.
What I mean by this? That it is likely that if hospitals throughout the world take this into account and the updated protocols for a normal delivery begin to be followed more and more (as we have in Spain, for example), cesarean deliveries will begin to decrease , will increase the confidence of women in their birth process (right now many will give birth without knowing very well what will happen, simply doing what they are told to do, instead of being prepared and aware of what will happen) and you will probably consider that cephalopelvic disproportion is a very rare condition actually.
Photos | iStock
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