Current study caesarean risk of women inheritable?

Mothers give caesarean risk to their daughters

Girls who were born by caesarean section will later give birth to their child in this way with a much higher probability than those who were born naturally. Researchers from Austria have now calculated this.

How the expectant mother was born

Although it was reported a few years ago that there are more and more caesarean births and almost every third birth takes place in Germany in this way, but now the numbers are slightly declining in this country. According to experts, the rate should be lowered even further, because "every caesarean section is an operation and should only be performed if it is medically necessary," said the German Midwives Association (DHV) in a statement. Whether a Caesarean section is necessary, apparently also depends on how the expectant mother was born.

According to researchers, women who were born by Caesarean section due to a craniocerebral pelvic imbalance of their mother more than twice as likely to have a mismatch in the birth of their children than those born naturally. (Image: nerudol / fotolia.com)

Evolutionary anatomical change

Women who were born by caesarean section due to their mother's craniocerebral pelvic disproportion develop more than twice as often a mismatch in the birth of their children than those born naturally.

This is the conclusion reached by evolutionary biologists from the University of Vienna around Philipp Mitteröcker, who explained in a mathematical model the seemingly paradoxical phenomenon that the rate of birth problems could not be reduced by natural selection, a communication states.

The data also support the thesis that the regular use of caesarean sections has already led to an evolutionary anatomical change. Your calculations are currently published in the journal "PNAS".

Number of caesarean sections multiplied

In most countries, the number of caesarean sections has multiplied in recent decades, so today the caesarean section (Latin for cesarean section) is one of the most commonly performed operations.

Experts believe that this is a social phenomenon, because the rate of actual birth problems - especially the so-called "pelvic head disproportion" (note: the child's head does not fit through the birth canal) - is many times lower.

Philipp Mitteröcker from the Department of Theoretical Biology at the University of Vienna asked himself why evolution did not lead to a larger birth canal and thus to more secure births.

Survival of a baby

In a study from 2016, the evolutionary biologist explained this seemingly paradoxical situation with a population genetic-mathematical model as a kind of "fitness dilemma".

"From an evolutionary point of view, a narrow pelvis is an advantage: on the one hand for our locomotion, but also because it can lead to uterine prolapse and other pelvic floor problems in very large pelvis at birth," says Mitteröcker.

On the other hand, the greater the chances of survival of a baby, the greater it is at birth. Here, therefore, the selective pressure towards narrower pelvis and that towards larger babies get in the way, so to speak.

"For our fitness curve, this means that the narrower the pelvis and the bigger the child, the better - but only to the point where the child can no longer fit in. Then it will be abruptly fatal," explained the expert.

Birth problems due to a skull-pelvic disproportion

Due to this unusual selection process, the rate of birth problems can not be reduced by natural selection. Furthermore, the researchers were able to show through their model that the regular use of life-saving Caesarean sections in the last 50 to 60 years has already caused an evolutionary change of anatomical dimensions.

This in turn has increased the incidence of birth problems by a craniocerebral imbalance by ten to 20 percent.

However, this predicted increase in craniocerebral palsy is hardly empirically provable, since such a mismatch is very difficult to diagnose.

The rate of caesarean section as an indirect measure has in turn increased significantly more for many other, non-medical reasons.

"The increase in caesarean sections is indeed a social phenomenon, but not only: the birth problem has also increased, albeit to a much lesser extent than the caesarian sections," explained Mitteröcker.

Birth problems and caesarean section studied over two generations

In the current PNAS study, the scientists now show that the "cliff edge model" also predicts that women who were born by caesarean section themselves due to a craniocerebral pelvic disproportion more than twice as often a mismatch at birth develop their children as women who were born naturally.

This considerable effect should be easier to recognize in epidemiological data than the evolutionary increase.

"In fact, we found empirical studies that examined birth problems and caesarean sections over two generations. The predicted 'heredity' of craniocerebral palsy and caesarean section is surprisingly well confirmed by these studies, "said Mitteröcker.

This theoretical prediction of a complex epidemiological pattern thus also provides independent confirmation of the cliff-edge model and its evolutionary implication. (Ad)