Caesarian Births Cause Evolutionary Changes In Humans

The regular use of Caesarean sections (C-section) affects human evolution by narrowing the pelvis of mothers, scientists found.

More mothers today need surgery to deliver a baby due to their narrow pelvis size. The researchers in Austria found that the trend is likely to continue, but not to the extent that normal spontaneous deliveries become obsolete.

The rise of Caesarean births in the recent decades may have contributed to a bigger gap between the size of newborns and their mothers' pelvises. The researchers estimated that the regular use of C-sections has led to the 10 to 20 percent increase in the said gap.

"Evolution is happening even in our modern society," Philipp Mitteroecker, an assistant professor in the Department of Theoretical Biology at the University of Vienna, Austria, said as reported by CBS News.

However, despite the changes in the size of babies being born, the size of the pelvis of mothers remained small.

"Without modern medical intervention such problems often were lethal and this is, from an evolutionary perspective, selection. 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," he added.

According to BBC, the number of Caesarean cases of babies who cannot fit down the birth canal has increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.

About 32 percent of all deliveries in the United States alone are done through C-section, the Centers for Disease and Control Prevention (CDC) said. In all, there were more than 2.6 million vaginal deliveries and 1.2 million Caesarean deliveries in 2014.

In the past, C-sections are done only when the mother's or the baby's life is in danger. However, as they have become more common across the globe over the past years, it has stirred debates on whether the procedure is a necessary one or an elective or optional one.