As Americans have grown fatter over the last generation, inviting more heart disease, diabetes and premature deaths, all that extra weight has also become a burden in the maternity ward, where babies take their first breath of life.

About one in five women are obese when they become pregnant, meaning they have a body mass index of at least 30, as would a 5-foot-5 woman weighing 180 pounds, according to researchers with the federal Centers for Disease Control and Prevention. And medical evidence suggests that obesity might be contributing to record-high rates of Caesarean sections and leading to more birth defects and deaths for mothers and babies.

Hospitals, especially in poor neighborhoods, have been forced to adjust. They are buying longer surgical instruments, more sophisticated fetal testing machines and bigger beds. They are holding sensitivity training for staff members and counseling women about losing weight, or even having bariatric surgery, before they become pregnant.

At Maimonides Medical Center in Brooklyn, where 38 percent of women giving birth are obese, Patricia Garcia had to be admitted after she had a stroke, part of a constellation of illnesses related to her weight, including diabetes and weak kidneys.