How to Help a Baby Gain Weight While 31 Weeks Pregnant
You're approaching the home stretch now, and at 31 weeks, your unborn baby continues to grow at an astonishing speed.
Not all babies gain weight at the same pace, and your obstetrician may have told you that your baby is smaller than average. While nothing should take the place of adequate prenatal care, healthy habits can also play a role in increasing your baby's weight.
What's Normal at 31 Weeks
When you reach the 31-week mark of your pregnancy, your baby will be about 15.5 inches long and weigh between 3.5 and 4 pounds, according to the American Pregnancy Association.
During the several weeks you have left before delivering your baby, she'll likely gain at least 3 more pounds, and possibly more. She'll also increase in length by about 4 to 5.5 inches. As your baby grows, she will develop a layer of fat under her skin, which prepares her for birth, the American Pregnancy Association notes.
Increase Your Calories

Does Diet Affect Having a Large Baby?
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Nutrition is key during pregnancy. The foods you eat play a direct role in your baby's growth and development. Eating a well-balanced diet that includes a variety of fruits, vegetables, grains, lean meat and dairy foods ensures that your unborn baby is getting each of the nutrients she needs to grow. During the third trimester, which is the last three months of pregnancy, you'll need to eat about 300 additional calories per day to promote normal growth, according to the American Pregnancy Association. Of course, you should increase your caloric intake with nutrient dense foods, and avoid high calorie foods such as cake, soda and fast food because they don't supply your baby with essential nutrients.
Eat Healthy Fats
Many people fear fat, but you actually need fat in your diet to promote the proper absorption of nutrients.
This is particularly important during pregnancy when your unborn baby is relying on your fat intake to get the vitamins and minerals she needs to grow and develop normally.
This doesn't mean that you have a free pass to eat whatever you want, but adding foods with unsaturated fats might help your baby grow and will also ensure that your placenta is healthy, according to the American College of Obstetricians and Gynecologists. Avocados, nuts, seeds, olive oil and fatty fish such as salmon, are all good choices for increasing your intake of healthy fats.
More to Do

Diet During the 32nd Week of Pregnancy
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Get adequate prenatal care in addition to eating a healthy diet. If you see your obstetrician regularly, she can keep an eye on your pregnancy and provide recommendations to help your baby grow. Aside from eating a healthy diet, certain lifestyle factors can inhibit growth, as well.
Don't smoke, drink alcohol or use drugs while you're pregnant, because they are associated with low birth weight, according to the March of Dimes. Additionally, if you and your partner are small people, your baby will likely be small, as well, and this isn't necessarily a problem, as long as you're following your doctor's eating and health recommendations.