The larger a pregnant woman is when she checks in on delivery day, the greater her risk of having a cesarean section, suggests a large new study. Nearly one of every three births in the U.S. is now delivered by cesarean, a surgery that has been linked to complications for both mom and baby such as infection, bleeding and hysterectomy. This rate is about 50 percent higher than it was in the mid-1990s, according to the U.S. Centers for Disease Control and Prevention. "As clinicians, we are faced with so many issues when taking care of patients with higher BMI, and one of them is a greater risk for cesarean," lead researcher Michelle Kominiarek, MD, of Indiana University told Reuters Health. She added that while previous studies had already linked cesarean delivery and body mass index -- a measure of weight that takes into account height -- none had been large or detailed enough to determine how other factors might alter that risk, such as prior births or cesarean sections.