She now encourages other doctors to counsel patients on nutrition and wants the Institute of Medicine to change its recommendations on weight gain.
The institute has not been formally charged by a federal agency or outside group to revisit the guidelines, a requisite for a new study. But the body of research doesn't yet show that gaining no weight is safe and effective, said Kathleen M. Rasmussen, professor of nutrition at Cornell University and chair of the committee that conducted the last review.
"However, doctors can certainly still apply their best clinical judgment for a given case and provide nutritional support for a heavier woman to gain less," she said.
Another committee member also questioned the safety of weight loss. Doctors should continue to follow the guidelines until further research is available, said Dr. Patrick M. Catalano, chairman of the Department of Obstetrics and Gynecology at Case Western University at MetroHealth Medical Center in Cleveland.
But Thornton argues that studies already show a better diet, with or without weight loss, is safe.
A recent study conducted in Europe and published in BMJ Journals concluded obese women could diet safely with the direction of health professionals. And calorie restriction was more effective than exercise to control weight gain.
The study found that women who restricted their calories were a third less likely to develop pre-eclampsia, among the most dangerous complications because it can severely raise blood pressure. The women were also 60 percent less likely to develop gestational diabetes, 70 percent less likely to have high blood pressure and 32 percent less likely to deliver early. Babies' birth weights were not affected.
Such information may be motivational to pregnant women, but the study's authors acknowledged changing eating habits is hard. Indeed, the CDC says 57 percent of obese women gained excessive weight in pregnancy, or more than 20 pounds above current recommendations.
Eddins said it was hard to change after a lifetime of poor eating choices. But she plans to continue losing weight after the baby is born.
"At first I was surprised they didn't want me to gain any weight," she said of doctors' advice. "But now I eat strawberries, bananas and grapes. I drink milk, I eat chicken. I feel good. … I have the willpower because I want to do what's healthy for my baby."
Ideally, doctors say women such as Eddins should be counseled on weight and nutrition before they become pregnant, though about half of pregnancies are unplanned.
That's the ideal time to lose weight, though many women will think "why bother" because they will be gaining weight in pregnancy, said Dr. Roxanne Jamshidi, a Johns Hopkins Bayview obstetrician.
Jamshidi is among the doctors recommending that some women who can't lose weight another way have bariatric surgery before conception. The surgery can increase fertility, and some may need it to become pregnant, she said. The surgical procedures include a band on the stomach or gastric bypass and can quickly restore normal ovulation and conception chances, she said.
A recent study in which Jamshidi participated also showed the surgery reduced pregnancy complications.
"Many women have already failed with other weight loss attempts," she said. "For some, surgery is the only thing that works. … Even if they are still obese, but they're 100 pounds less obese, they do better in pregnancy."