According to a recent study, nearly one third of American babies are born by cesarean section. This type of birth seems to be affecting the gene pool of humans in ways that many didn’t expect. More children with heads too large to fit through the birth canal are being delivered by c-section. A bigger head is healthier, but these children may not have survived even 50 years ago. On the other side of the spectrum, women with smaller pelvis openings are able to deliver babies with less mortality. We may see the c-section rate continue to increase even more.

Key Takeaways:

• With cesarean sections on the rise in recent years, roughly one in three U.S. babies are now born via surgical delivery.
• To oversimplify things, c-sections have led to smaller pelvises and bigger babies, resulting in more c-sections. But this isn’t to say they will eventually outnumber vaginal births.
• C-sections are unavoidable in many cases because of increasing rates of mom-baby size incompatibility, among other factors. And there’s absolutely no shame in that.

“This is generally a positive/healthier thing, except a bigger head also means babies have more trouble fitting in the birth canal. Now, newborns that would have gotten stuck and died in childbirth 100 years ago are surviving thanks to c-sections.”

http://blogs.babycenter.com/mom_stories/how-c-sections-might-be-affecting-human-evolution/