A new study has suggested that an increased number of cesarean sections (C-sections) being performed is giving rise to changes in women's biological physiology. The study suggests that the operations are, in turn, shaping human evolution.

According to Sky News, researchers estimate that three to six percent of births are through C-section due to the fact that the mothers' pelvis are too small for the head and shoulders of the child to pass through. While the C-section procedure dates back to ancient times, it is being performed very frequently in recent times. 

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In the United States of America, C-section births numbered about five percent in the 1970s. The same figure has increased by more than a quarter during the last 30 years. The NHS in the United Kingdom has reported similar figures as well.

A study conducted by a team of researchers from the US and Austria used mathematical models to demonstrate their theory. The scientists used calculations to prove that the increased use of cesarean operations has resulted in an increase in the size of babies relative to a women's pelvic birth canal.

Dr. Philipp Mitteroecker at the University of Vienna told the BBC that it has been a long-standing question in human evolution as to how the size of women's pelvises and the size of babies' heads were finely balanced through the ages.

"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," Dr. Mitteroecker said.

The scientists used data provided by the World Health Organisation to calculate that the global rate of cases where the baby's head was too big to fit through the maternal birth canal was 30 in 1,000 births. The researchers estimate that in the past 60 years, the rate has increased by three percent.

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