"While we don't know the exact reason, it's possible that obesity contributes to a problem with blood-sugar control," says Carmichael. High-glycemic foods tend to make blood sugar soar; in contrast, the unrefined carbohydrates in fiber-rich whole grains, beans, and vegetables result in a slower release of sugar into the blood and help you feel full longer. "We don't want to be alarmist -- eating a sandwich on white bread will not hurt your baby. Still, the best route during pregnancy is to follow the recommendations of eating high-fiber, less-processed, and calcium-rich foods, as well as fruits and vegetables."
A study published in the May 2003 issue of Pediatrics entitled "Maternal Influences on Child Health," had similar conclusions: It found a link not just between obesity and neural tube defects but also between being overweight and an increase in congenital heart problems as well as "multiple defects" (when a child suffers from more than one major malformation).
Heavy women are more likely to have a cesarean delivery. Another study in Pediatrics found that women who gain excess weight during pregnancy account for a growing proportion of cesarean deliveries (which are now up to 26 percent nationwide, according to the CDC, the highest ever recorded) because excess weight is associated with overly large fetuses that can't be delivered vaginally. Gestational diabetes (more common in heavier women) can also cause the fetus to grow too large. "Bigger babies are at higher risk of experiencing shoulder distocia during delivery -- the head may make it out, but the shoulders get stuck," notes Marcos Pupkin, M.D., chairman of obstetrics and gynecology at Mercy Medical Center, in Baltimore. "Then, we are forced to try to reposition the fetus, which can cause trauma to the baby. In some cases, we must do a cesarean, and there is a greater risk of infection to the mother because there are so many more layers of fat to cut through." Even in the best circumstances, c-sections are considered major surgery and incur risks for the mother, including complications from more extensive anesthesia and the possibility of hemorrhage due to a surgical accident, not to mention a longer and more painful recovery period.
Being overweight or obese compromises a woman's future health. Heavy women have a higher risk of heart disease, diabetes, certain cancers, and arthritis. Postpartum, a heavy woman is much more likely to retain the excess weight, compounding the problem with each successive pregnancy. "Women who gain more than the recommended amount during pregnancy are more than four times as likely to be obese one year after giving birth," says Christine Olson, Ph.D., professor of nutritional sciences at Cornell.