RALEIGH, N.C. — When I learned I was pregnant last fall, I made a promise to myself: I would not pack on the pounds and wave goodbye to my favorite jeans forever.

But secretly, I was nervous.

The reality is that many women gain far too much while pregnant. One in four expectant mothers puts on 40 pounds or more, according to the Institute of Medicine. That's well over the 25 to 35 pounds the institute, which advises the federal government, recommends as a healthy target for a woman starting out at a normal body mass.

And now medical experts are starting to question whether the recommended gain may be too much, leading to lasting weight problems for both mother and child. An Institute of Medicine panel expects to meet this fall to begin discussing whether its recommendations, which have been in place since 1990, should be reduced.

It's worth noting that most of the recommended 25 to 35 pregnancy pounds aren't fat. The bulk of the extra weight is made up of fluids, the baby and tissues such as the placenta, which are usually subtracted from the number on the scale within a couple of weeks of delivery. A woman who gains within the recommended range typically has less than 10 pounds of fat to lose post-baby.

But I didn't know all of that when I was newly pregnant. Since I was already at a healthy weight, I figured I'd shoot for the middle — 30 pounds.

I found surprisingly little guidance on how to achieve that goal. The literature my obstetrician's office gave me mostly emphasized what foods to avoid.

I was pleasantly surprised when I learned, from a variety of pregnancy books and Web sites, that it takes just 300 calories on top of an adequate pre-pregnancy diet to support the healthy development of a growing fetus. That reassured me that I wouldn't be preserving my figure at the expense of my baby.

I planned to keep eating the same healthy diet of mostly lean meats, fruits and vegetables and whole grains I already followed and work in the extra food with a couple of 150-calorie snacks. A piece of fruit and a stick of string cheese is about that much, for example. Or I could eat a small extra meal, such as a small bowl of tomato soup, whole grain crackers and a small apple, and get all 300 at once.

I did not consult a professional nutritionist when planning my pregnancy diet, but Lisa Martin, a Raleigh, N.C., registered dietitian, assured me that my approach of small frequent meals was sound.

"You kind of want to graze all day during pregnancy," said Martin, who, as a mother of four has gained — and lost — about 150 pounds during three pregnancies, including 85 pounds during a difficult pregnancy with twins.

Martin said small meals help pregnant women, whose digestive tracts slow to allow for better absorption of nutrients and to cope with reflux and indigestion. Eating often also helps keep nausea at bay.

"A lot of times when women feel sick it's because they don't have enough food on their stomachs," Martin said.

While it's probably not strictly necessary to try to get 100 percent of your nutritional needs during pregnancy through food — obstetricians and midwives will prescribe a good prenatal vitamin to ensure adequate levels of essential vitamins and minerals — it's smart to eat healthfully while expecting, Martin said.

Eating iron-rich foods such as lean red meat, poultry and dark green vegetables can help stave off fatigue during pregnancy. Choosing foods that are high in fiber will help keep that sluggish digestive system moving. And calcium is important to build baby's bones and teeth. Martin notes that the baby will take any needed nutrients not supplied by food and supplements directly from your body's existing nutrient stores. That can leave a new mom feeling run-down just as she's called to 24-7 baby duty.

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