By Lisa Rapaport
(Reuters Health) - While cesarean deliveries are often necessary to save lives and prevent injuries, being born by C-section may also leave babies vulnerable to chronic health problems such as asthma, diabetes and obesity, a new analysis suggests.
Much of the research included in the study cannot prove these surgical deliveries cause medical issues later in life. But the link is strong enough that mothers should discuss the risk with their doctor or midwife when weighing whether to proceed with a C-section, particularly when a vaginal delivery may be possible, said lead study author Dr. Jan Blustein.
"It's a discussion that's important to have in view of the rising rate of C-sections," said Blustein, a professor of medicine and health policy at New York University. "The magnitude of risk elevation is small, but even when we are talking about increasing the risk modestly, we still need to talk about it."
Ideally, no more than 15 percent of deliveries should be C-sections, according to the World Health Organization. That's the approximate proportion of births that require surgical intervention to protect the mother or infant in situations such as prolonged labor, fetal distress or a breech baby.
In many countries - including the U.S., Mexico, Brazil, Australia and Italy - C-section rates are more than double the level WHO recommends.
Blustein and co-author Jianmeng Liu of the Institute of Reproductive and Child Health in Beijing write in The BMJ that C-section rates are unnecessarily high in some countries in part because some surgical deliveries are elective, done only because women requested them, and because mothers who have one C-section are often encouraged to deliver this way again.
When they analyzed past research, they found 20 studies linking C-sections to childhood type 1 diabetes. They also found 23 studies connecting surgical deliveries to asthma and nine suggesting a tie to obesity.
In the U.S., where about one third of deliveries are by C-section, 2.13 of every 1,000 babies born this way develop type 1 diabetes, compared with 1.79 per 1,000 infants delivered vaginally, the study found.
About 9.5 percent of C-section babies develop asthma, compared with 7.9 percent for vaginal births. Obesity develops in 19.4 percent of children delivered by C-section, compared with just 15.8 percent for vaginal births, the study found.
Why C-sections might lead to chronic health problems isn't clearly established, but one prevailing theory is that women may pass "good" bacteria to babies during a vaginal delivery that protects against disease, Blustein said. Another possibility is that hormones released during labor might play a role in minimizing risk, she said.
Most of the studies included in the analysis did not have enough information for researchers to account for characteristics of mothers, such as obesity, that might precipitate C-section delivery or be linked to the child's later health problems, the study authors caution.
Based on the mounting evidence linking C-sections to chronic health problems, however, the authors recommend that the American College of Obstetricians and Gynecologists (ACOG) and the U.K.'s National Institute for Health and Care Excellence revise practice guidelines to include the long-term risk of chronic disease.
Last year, ACOG issued new guidelines aimed at reducing unnecessary C-sections by encouraging doctors to let labor progress longer and consider non-surgical options to help women deliver vaginally.
"While cesarean deliveries can be life-saving for both mother and baby, cesareans can also lead to short-term and long-term complications for both," ACOG president Dr. Mark DeFrancesco said in an emailed statement.
More research is needed, however, to show whether the C-section itself or other factors might contribute to long-term health problems in babies born this way, he said.
Even so, the current study adds to a growing body of evidence suggesting that the mode of delivery might have lasting health implications, said Dr. Susan Hellerstein, an obstetrician at Harvard Medical School and Brigham and Women's Hospital in Boston.
"It is a large number of observational studies that are all pointing in the same direction," said Hellerstein, who wasn't involved in the current study. "We should be having a conversation with patients about the risk when they are considering a truly elective c-section."
SOURCE: http://bit.ly/1Gzdjj0 British Medical Journal, online June 10, 2015.