That's a tall order, considering that about 55 percent of women of childbearing age are overweight and preconception care isn't that common.
Once a woman's pregnant, the guidelines issued Thursday aren't too different from what obstetricians already recommend -- but they're not easy, considering about half of women fail to follow them today.
Among the advice:
--A normal-weight woman, as measured by BMI or body mass index, should gain between 25 and 35 pounds during pregnancy. A normal BMI, a measure of weight for height, is between 18.5 and 24.9.
--An overweight woman -- BMI 25 to 29.9 -- should gain 15 to 25 pounds during pregnancy.
--An obese woman -- BMI of 30 or higher -- should gain 11 to 20 pounds. This marks the first recommendation ever set for women so heavy.
--An underweight woman -- BMI less than 18.5 -- should gain 28 to 40 pounds.
What if a mom-to-be has already gained too much? On average, overweight and obese women already are gaining five more pounds than the upper limit.
But pregnancy is not a time to lose weight, stressed guidelines co-author Dr. Anna Maria Siega-Riz of the University of North Carolina, Chapel Hill.
"It's not, 'Hey you gained enough, now you need to stop,"' Siega-Riz said. "Let's take stock of where you're at and start gaining correctly."
Indeed, the guidelines lay out that in the second and third trimesters, underweight and normal-weight mothers should be putting on a pound a week for proper fetal growth. The overweight and obese need about half a pound a week.
Hopping on the scale during prenatal checkups makes for a sensitive moment, especially in a culture that cherishes the ice cream-and-pickles stereotype.
Implementing the guidelines may take a move "to change the whole culture about pregnancy" and eating, Siega-Riz said. She noted that in studies of the overweight, "most of these women will tell you that they've never been told how much weight to gain" during pregnancy.