Obesity is on the rise for all Americans, including women of reproductive age. Health providers assess the degree of obesity using a calculation called the body mass index, or BMI—a calculation incorporating your height and weight. Your BMI should be calculated using your non-pregnant weight. Your BMI can be calculated for you at nhlbisupport.com/bmi/.

BMI is classified as follows: normal weight (BMI 18.5 to 24.9), overweight (BMI 25.0 to 29.9), obese (BMI 30.0 to 34.9), very obese (BMI 35.0 to 39.9), and extremely obese (BMI 40.0 or higher).

Increased Pregnancy Complications
Women with a body mass index (BMI) over 24.9 have a higher rate of pregnancy complications. These include gestational diabetes, pregnancy-induced hypertension and pre-eclampsia. As an example, obesity causes a five-fold increased risk of developing gestational diabetes. Additionally, overweight women are four times more likely than their normal weight counterparts to require a hospitalization during pregnancy, and are more likely to have an extended hospital stay at the time of delivery.

Increased Birth Defects
Infants of obese mothers are also at higher risk. The March of Dimes reported that obese and overweight women have a 30 to 40 percent higher chance of delivering a baby with a major birth defect affecting the brain, heart or gastrointestinal system. This includes a higher risk of neural tube defects. Studies have also linked obesity to a higher risk of stillbirth.

Increased Delivery Complications
Overweight and obese women are more likely to have a complicated delivery as well. On average, obese women progress more slowly in labor and have a higher risk of Caesarean birth. This may be in part because infants of obese mothers are more likely to be large for their gestational age, making natural delivery more challenging. There's also a higher chance of newborn complications and admission to a neonatal intensive care unit.

Long-Term Risks
Children of obese mothers may endure long-term health consequences, including obesity. Studies have indicated that children of obese mothers are three times more likely to become obese during childhood and adolescence, putting them at risk for a host of associated health problems.

What to Do if you are Overweight
If you are not yet pregnant, meet with your healthcare provider to come up with strategies to lose weight before pregnancy. This is the best time to lose weight, as weight loss is not recommended during pregnancy. Most weight loss programs combine strategies to lower calorie intake and increasing activity levels. It's never easy to lose weight, but many women who plan to become pregnant find extra motivation to stick to weight loss regimes. It's also important to take a prenatal vitamin with folic acid. If you have a BMI greater than 35, 5 milligrams of folic acid a day is recommended to reduce the risk of birth defects.

If you are already pregnant and know that you are overweight, talk to your doctor about ways to achieve the healthiest pregnancy outcome. Your doctor may encourage you to exercise regularly. Daily activities such as walking, swimming and prenatal water aerobics can increase your energy and endurance, help you minimize further weight gain, and keep your blood sugar level in normal range. However, it's important to do things in moderation when you're pregnant. Be sure to warm up before you exercise, drink plenty of water while exercising and avoid overexertion.

Limit Weight Gain During Pregnancy
Women who begin pregnancy substantially overweight do not need to gain as much weight during pregnancy as women of normal weight. Aim to gain between 15 to 25 pounds if you're overweight but not obese, and no more than 15 pounds if your BMI classifies you as obese.

However, avoid strict dieting. Pregnancy is not the time to try to lose weight. Instead, pack your diet with nutrient-dense foods rather than ones with empty calories. Healthy choices include lean meats and proteins, low-fat or non-fat milk, cottage cheese or yogurt, whole grains, and fresh fruits and vegetables. Avoid fruit juices, sodas and sugared drinks, which pack on unnecessary calories. Instead, drink low-fat milk and plenty of water. Similarly, choose raw vegetables and high-protein snacks rather than sugared or high fat alternatives. I recommend meeting with a nutritionist early in your pregnancy to devise an appropriate meal plan. And remember to take a prenatal vitamin with folic acid every day.

Adhere to Prenatal Care and Diagnostic Tests
Finally, it's important to keep up with your prenatal care. Regular prenatal visits and appropriate tests will help your doctor monitor your pregnancy and decide whether special care is necessary to ensure the healthiest outcome for you and your baby.