While a cesarean delivery is sometimes necessary and can be lifesaving, it may have serious long-term disadvantages for both mother and child, researchers report.

The analysis, in PLOS Medicine, pooled data from 80 studies including almost 30 million subjects.

Compared to vaginal delivery, C-sections were associated with a significant reduction in the risk for urinary incontinence and for pelvic organ prolapse, a dangerous weakening of the muscles that hold pelvic organs in place.

But for a pregnancy following a cesarean, there was a 17 percent increased probability of miscarriage and a 27 percent increased probability of stillbirth. The researchers also found nearly triple the probability for placenta accreta, in which the placenta grows too deeply into the uterine wall, and an increased chance of other placental problems.

Children delivered by cesarean had a 21 percent increased probability of asthma by age 12 and a nearly 60 percent increased likelihood of obesity up to age 5.