Bigger newborn heads, same size pelvises for moms. That's what a new study is claiming C-sections are causing, since this form of childbirth has been steadily on the rise since the 1950s in the U.S.
More babies are being born with bigger craniums, yet the mother's bodies are not adapting accordingly, thus creating the need for C-sections to be the necessary or preferred delivery option for even more moms, perpetuating the cycle.
The lead author of the study, Dr. Philipp Mitteroecker of the Department of Theoretical Biology at the University of Vienna, told BBC news, ""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. One side of this selective force - namely the trend towards smaller babies - has vanished due to Caesarean sections." Mitteroecker notes, "I expect that this evolutionary trend will continue but perhaps only slightly and slowly," so mothers of the future need not be alarmed that no babies will be able to be delivered vaginally any time soon or ever for that matter.
Some causes for this increase in C-sections include diabetes in young mothers, higher rates of obesity in mothers, and women giving birth later in life, among other pre-natal and delivery complications. Other moms-to-be opt for elective surgery rather than deliver naturally.
Human newborns have large heads compared to other primates, according to the Proceedings of the National Academy of Sciences of the United States of America (PNAS). "Human childbirth is difficult because the fetus is large relative to the maternal pelvic canal. It is a long-standing evolutionary puzzle why the pelvis has not evolved to be wider, thus reducing the risk of obstructed labor."
With the findings from this study, the rates of fetopelvic disproportion will only increase. Medical advancements will always find a way to make childbirth safer, particularly in countries with modernized medical availability. Until (or if ever) the female human body adapts evolutionarily, the C-section rates will inevitably continue to increase as newborns' heads expand in size.