The number of women having cesarean sections (c-sections) has spiked in recent decades because improved living conditions are making babies bigger, according to scientists.
Compared to other mammals the size of a human baby’s head compared with an expectant mother’s pelvis can make labor particularly tough. In around 5 percent of pregnancies in the U.S. involving children weighing 4 kilograms or more, the head is too big to pass through the mother’s birth canal, the authors of the study explained in their study, published in the journal Proceedings of the Royal Society B. Undergoing a c-section is one way to get around this.
But the number of c-sections are higher than the women experiencing what is known as cephalopelvic disproportion. The procedure may also be carried out when the head and birth canal are an almost too tight fit; or because the woman is suffering from mental conditions such as anxiety. And the rates of c-sections vary wildly in different countries—from as low as 2 percent in some parts of sub-Saharan Africa to around 50 percent of mothers in Egypt, Brazil and Turkey. In the U.S., some 33 percent of babies were born via c-section between 1996 to 2011, according to the Centers for Disease Control and Prevention.
“The stark difference in c-section rates are commonly attributed to socioeconomic and cultural factors (including access to health care) only,” Dr. Philipp Mitteröcker, associate professor of theoretical biology at the University of Vienna, told Newsweek. The scientists set out to uncover any other reasons.
The researchers analyzed data from governments and global health bodies like the World Health Organization to calculate the number of c-sections which had taken place in each country, as well as the average heights of women, the size of babies.
“If there’s a strong body size increase due to environmental improvements, which are very well documented, then the neonate [unborn child], which is a generation ahead of the mother, might have experienced even better nutrition and environment than the mother did, which would on average lead to a slightly over proportionate size of the fetus in relation to the mother,” said Mitteröcker.
“This, in turn, would increase the average difficulty and length of childbirth and thus the rate of c-section. Hence, the actual difficulty and risk of childbirth are likely to vary globally.”
So, will this explanation wear away at the stigma towards c-sections? Women can be dubbed as “lazy,” and research has shown they can feel judged for opting for this form of delivery. There are also concerns that planned c-sections can lead to health problems in babies.
Mitteröcker stated that, while the work doesn’t provide any evidence in this area, it’s his personal belief that women should not feel ashamed about having a c-section, although it shouldn’t be the “default mode” of delivery. In fact, his own children were born via c-section, he said.
“The fit between the fetus and the birth canal—and thus the difficulty and risk of labor—clearly varies between individuals and also between geographic regions. Safety and health of the baby and the mother have priority, so c-sections are clearly indicated in certain cases,” he said. “In other cases it is less clear and pros and cons of c-section have to be discussed among obstetricians and the mother.”
More widely, the study shows that the human anatomy and physiology are not static, said Mitteröcker. “This can be important to improve medical treatment and plan public health policies.”
Last year, a separate study suggested doctors perform the procedure because they fear expectant mothers will sue them. The review of 34 studies conducted in 20 countries investigated the biggest concerns of health care professionals. It was published in the journal PLOS One.