SOURCES: Mairead Black, M.R.C.O.G., clinical lecturer and research fellow in obstetrics, University of Aberdeen, U.K.; Mitchell Maiman, M.D., chairman, department of obstetrics and gynecology, Staten Island University Hospital, New York City; Thomas G Weiser, M.D., M.P.H., assistant professor, surgery, Stanford University School of Medicine, Stanford, Calif.; Dec. 1, 2015, Journal of the American Medical Association
TUESDAY, Dec. 1, 2015 (HealthDay News) -- Children born by planned cesarean delivery appear to have a slightly higher chance of developing asthma than those born through vaginal delivery, researchers report.
The difference in risk was small, with 3.73 percent of those born through planned C-section hospitalized by age 5 for asthma, compared to 3.41 percent of kids who were born through vaginal delivery. And those who had a cesarean delivery had a 10.3 percent risk of needing an asthma inhaler at age 5, compared to 9.6 percent for those born vaginally, the researchers found.
"C-section may play a part in explaining global increases in asthma, but overall this study provides some reassurance that children delivered by planned C-section are not at substantially higher risk of childhood illness," said lead researcher Dr. Mairead Black. Black is a clinical lecturer and research fellow in obstetrics at the University of Aberdeen, in Scotland.
"This is an observational study, so we cannot definitively say that the planned C-section is the cause of the small increase in risk of asthma," she said.
"The absolute difference in risk to children delivered by planned C-section was very low. So, while C-section may play a part in explaining global increases in asthma, it is unlikely to be important enough to influence individual delivery decisions," Black added.
The report was published Dec. 1 in the Journal of the American Medical Association.
For the study, Black and her colleagues collected data on more than 321,000 firstborns in Scotland between 1993 and 2007, and followed them until February 2015.
The investigators found that, compared with children born by emergency cesarean delivery, those born by planned cesarean delivery were not at a significantly increased risk for asthma requiring hospitalization, asthma inhaler prescription at age 5, obesity at age 5, inflammatory bowel disease, cancer or death. But they were at increased risk of type 1 diabetes, the findings showed.
Dr. Mitchell Maiman, chairman of the department of obstetrics and gynecology at Staten Island University Hospital in New York City, said, "C-section can be a disadvantage for babies."
The process of going through the birth canal may be a benefit to the infant's immune system, he suggested. "There's something about going through the birth canal -- the most difficult trip the child will have in its entire life -- that has a competitive advantage," Maiman said.
Maiman said having a C-section, unless it is medically necessary, is not recommended. For mothers, a C-section can increase the risks of bleeding, dying and having problems delivering the placenta. "A C-section is much less safe than a vaginal delivery," he added.
Another study in the same journal looked at C-section rates around the world, and found higher cesarean rates correlated with lower death rates among infants and new mothers. The rates of cesarean delivery vary widely from country to country, from as low as 2 percent to more than 50 percent, the researchers found.
"In countries that provide very low rates of C-sections, there are very high rates of maternal and neonatal deaths," said lead researcher Dr. Thomas Weiser, an assistant professor of surgery at Stanford University School of Medicine, in Stanford, Calif.
As the number of C-sections increases, the rates of maternal and neonatal deaths decrease, he said. But when the rate of C-sections reaches about 19 per 100 births, there are no further reductions in deaths, Weiser added.
"Countries that are trying to improve outcomes are going to have to consider C-section as part of comprehensive maternal care," he said. "Countries that have very low rates of C-sections are going to have to improve that in the context of overall health care."
But, "on that flip side, countries that have high rates of C-sections may have rates that are excessive," Weiser added.
Visit the U.S. Office on Women's Health for more about C-sections and labor and delivery.