New research suggests that the widespread use of C-section deliveries is affecting human evolution.

The use of C-section helps in delivery of babies too large to pass through the birth canal or with other complications. But this method has also resulted in ‘at risk’ genes of mothers with narrow pelvises being passed on to the next generation.

Earlier such a situation led to the death of both mother and baby, resulting in natural selection.

A C-section, or caesarean section, is a medical procedure in which an incision is made in the mother’s abdomen and uterus to allow for babies to safely be delivered. The surgery may be planned in advance, or result as a consequence of unforeseen complications. The surgery has significantly reduced infant and maternal mortality rates across the world. C-sections performed due to too narrow a birth canal have historically been rare, amounting to 30 cases in every 1000 deliveries. However, this advancement in the field of medicine is proving to have affected the natural evolutionary process. Research has emerged to suggest that this procedure is subverting the process of natural selection.

Dr. Philipp Mitteroecker, from the department of theoretical biology at the University of Vienna commented “Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters.” This has lead to cases involving babies too large to naturally pass through the vaginal cavity without seriously endangering the mother and the child increasing to 36 cases in every 1000, which is a 10 to 20 percent increase in the original rate.

This process of what he calls fetopelvic disproportion (narrow pelvis), is compounded by modern health issue epidemics such as obesity and diabetes. Daghni Rajasingam, of the Royal College of Obstetricians adds “I think what is important to take into the (question of) evolution is that things like diabetes are much more common at a younger age so we see many more women of reproductive age who have diabetes.”

Yet, Dr. Mitteroecker does point out that this trend will only continue slowly. Further saying “There are limits to that. So I don’t expect that one day the majority of children will have to be born by (Caesarean) sections.”

The research team used a mathematical model based on obstructed childbirth data to reach their estimates. And says more research is needed to link c-sections and narrow pelvis evolution conclusively.

The research is published in the journal, Proceedings of the National Academy of Sciences.