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C-section births linked to long-term child health problems

Newborn baby girl right after delivery.

Kati Molin

About a third of all babies in the U.S. are delivered by cesarean section. Now a new study has found that newborns delivered by C-section face an increased risk of a number of chronic health problems later in life.

The research, published in the British Medical Journal, found that newborns delivered by C-section are more likely to develop obesity, asthma, and type 1 diabetes when they get older.

In a meta-analysis of studies, Dr. Jan Blustein of New York University's School of Medicine and Dr. Jianmen Liu of Peking University found 20 studies that link C-sections to type 1 diabetes, 23 studies that suggested a tie with asthma and another nine that found an association with obesity.

In the U.S., the overall childhood asthma rate is 8.4 percent, which jumps to 9.5 percent among those born via C-section. The obesity rate among children delivered vaginally is 15.8 percent, versus 19.4 percent among kids born by C-section. Type 1 diabetes occurs in 2.13 of every 1,000 infants born from C-section, compared to 1.79 per 1,000 babies delivered vaginally.

"It is clear that cesarean-born children have worse health, but further research is needed to establish whether it is the cesarean that causes disease, or whether other factors are at play," Dr. Blustein said in a press release. "Getting definitive answers will take many years of further research. In the interim, we must make decisions based on the evidence that we have. To me, that evidence says that it is reasonable to believe that cesarean has the potential for long-term adverse health consequences for children."

Bluetein told CBS News, "People have always known the consequences of vaginal delivery -- brain damage, cerebral palsy, shoulder dystocia -- but there is not much discussion of the long-term downsides of cesarean delivery."

Blustein and Liu note that the newly found risks are not mentioned in clinical guidelines, the official documents that are used to educate doctors and midwives. The authors suggest that the guidelines should be updated to include information about possible risks to long-term child health.

They acknowledge that C-sections are medically necessary in some cases -- but not always. "In emergencies, or when a fetal or maternal indication is present, the choice is clear. But in cooler moments, such as repeat or maternal choice of caesarean, it makes sense to consider the risks and benefits," they write.

"In the moment," Blustein says, obstetricians "are more interested in getting a healthy baby out" than stopping to consider long-term health consequences. But in cases where C-section may be optional, "Our main message was that it's time for people who make guidelines to think about long-term child health and look at the evidence. We wanted to get the dialogue started."

More than 32 percent of pregnant women in America deliver by cesarean section, according to 2013 data by the Centers for Disease Control and Prevention. That number is well above the World Health Organization's target of 10 percent to 15 percent for medically necessary C-sections.

In 2014, new C-section guidelines from the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine raised concerns about the overuse of C-sections. The groups recommended that doctors should give otherwise healthy women more time to deliver their babies vaginally before opting to perform a C-section.

Blustein and Liu hope that eventually their research will have an impact on C-section guidelines. "It takes a while for research findings to reach clinicians and patients," Blustein said. "This research isn't widely known. It is time for that to change, so that doctors, midwives and patients can weigh the risks and benefits of elective cesarean, and decide accordingly."