FRIDAY, Feb. 11 (HealthDay News) -- Current U.S. guidelines may overestimate the amount of weight that severely obese women need to gain during pregnancy, according to a new study.

Extremely obese women who gained less than the Institute of Medicine-recommended amount of weight during the second and third trimester of pregnancy suffered no ill effects, nor did their babies, said the researchers at the University of Rochester Medical Center in Rochester, N.Y.

However, obese and non-obese women who gained less than the recommended amount of weight did experience problems, including a higher likelihood of delivering a baby that is small for gestational age.

The findings, scheduled to be presented Feb. 11 at the annual meeting of the Society for Maternal-Fetal Medicine, suggest a need to reconsider weight-gain recommendations for the most obese moms-to-be, the researchers said in a society news release.

The study included 73,977 women who gave birth to a single child. Four percent of the women were underweight; 48 percent normal weight; 24 percent overweight; 13 percent obese; 6 percent severely obese; and 5 percent morbidly obese.

The researchers also found that women in all weight categories who gained more weight than recommended in the second and third trimesters were more likely to have a baby that is large for gestational age.

In addition, overweight women who gained more than the recommended amount during pregnancy were more likely to have cesarean delivery, induced labor and gestational diabetes.

Experts note that research presented at meetings has not been subjected to the same type of rigorous scrutiny given to research published in peer-reviewed medical journals.

More information

The American Congress of Obstetricians and Gynecologists offers a pamphlet about nutrition during pregnancy.