decades ago, maternal-fetal medicine specialist Yvonne Thornton, M.D., was
determinedly shedding the 67 pounds she gained during her first pregnancy when
she found out she was expecting another baby. Thornton vowed not to let that
derail her healthy eating habits again. "There was a strong dictum back then
that no matter what you weighed, you should gain 26 to 35 pounds during
pregnancy or risk fetal death," says Thornton, now an OB-GYN professor at New
York Medical College. "But we put our diabetic pregnant patients on a sensible
diet that was safe, so I figured it was OK for me."
focused on eating healthfully and watching portion sizes, recording everything
she ate in a food journal. Her weight stayed steady at 222 pounds until she
delivered a healthy 8-pound, 8-ounce girl at 43 weeks. "I felt a hundred times
better than I did during my first pregnancy," she says. Two months later, she
was down to 160 pounds.
her own success, Thornton conducted a randomized clinical trial over several
years to show that emphasizing nutrition rather than weight would lead to
healthier pregnancies for obese women (those with a prepregnancy body-mass
index, or BMI, of 30
or higher). Her study of 232 such women found that those who followed a
doctor-monitored nutrition plan gained less weight, had fewer C-sections, were
less likely to develop gestational diabetes and retained less weight after delivery. Fifty-seven women
gained fewer than 10 pounds, and 23 of them lost weight during pregnancy with
no negative consequences.
monitor a mother's weight gain as a way to evaluate fetal growth, but regularly
measuring fundal height, the distance from the top of the mom's uterus to her
pubic bone, is a better indicator, Thornton maintains. When the Institute of
Medicine updated its pregnancy weight-gain guidelines in 2009, the authors said there was not enough data to support
recommending anything less than an 11- to 20-pound gain for obese women.
However, in a study of nearly 74,000 women presented at the Society for
Maternal-Fetal Medicine's annual meeting this past February, very obese women
(a BMI of 35 or higher) who gained fewer than 11 pounds suffered no ill
consequences—and neither did their babies. Those with a BMI of 30 to 34.9 who
gained fewer than 11 pounds did have a greater risk of delivering a
offers these suggestions for very heavy women: 1) Do not try to limit weight
gain without your doctor's supervision; 2) Weigh in only at prenatal visits,
and consider asking not to be told the results; 3) Eat twice as well, not twice
as much (but don't go under 2,000 high-quality calories a day); 4) Faithfully
keep a food journal (be honest!) and discuss it at prenatal visits.