How much weight should women gain while pregnant?

Back in the Dark Ages, when I was pregnant, doctors told women to gain 2 pounds a month, or 18 to 20 pounds in all. That worked fine for me and mine, and I didn't have tons of baby weight to lose afterward.

But in 1990, the gurus at the Institute of Medicine (part of the congressionally created National Academy of Sciences) got worried about low birth weight babies and came up with guidelines that said that skinny women (who have a BMI, or body mass index, of less than 19.8) should gain 28 to 40 pounds. Normal women (BMI of 19.8 to 26.0) should gain 25 to 35 pounds, and heavy women (BMI of more than 26.0) should gain the least, 15 to 25 pounds.

Enter the obesity epidemic. A whopping 66 percent of adult Americans are now overweight, according to the National Center for Health Statistics. "The number of obese pregnant women is rising, too," said Dr. Laura Riley, an obstetrician who is director of labor and delivery at Massachusetts General Hospital.

Starting a pregnancy when you are already obese and then gaining too much weight during the pregnancy raises many health risks, including the risk of hypertension and diabetes, said Riley, who chairs the Clinical Document Review Panel on Obstetrics for the American College of Obstetricians and Gynecologists.

So the Institute of Medicine is at it again, working on new guidelines, due out next year, that will consider obesity as well as other factors, including the age of the mother (the risks are higher at the extremes of the childbearing years), race, ethnicity, and height, said Ann Yaktine, a biochemist and nutritionist who heads the institute's guidelines effort.

In the meantime, said Riley of Mass. General, pregnant women should stick to the old weight gain guidelines, but aim for the lower figure in the ranges.

JUDY FOREMAN

E-mail health questions to foreman@globe.com.