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Obesity does not appear to increase the risk of preterm labor (labor before 37 completed weeks of pregnancy), which often results in premature birth (birth before 37 completed weeks of pregnancy) (4). However, obesity does increase the risk of pregnancy complications, such as preeclampsia, that sometimes make it necessary to deliver the baby before term. Premature babies are at increased risk of newborn health problems and lasting disabilities.
Does obesity in pregnancy pose a risk to the baby?
Most babies of obese women are healthy. However, obesity during pregnancy can increase the risk of a number of complications in the fetus and newborn. These risks include (3, 4, 5):
What can an obese woman do before pregnancy to improve her chances of having a healthy pregnancy?
A woman who is obese should discuss her weight with her health care provider before pregnancy. Her provider can help her determine a healthy weight to work towards before she tries to conceive. Her provider also can give her advice on a diet and exercise program. Obese women who lose weight before pregnancy reduce their risk of complications and improve their chances of conceiving.
Women who are obese are at increased risk of developing diabetes, both before and during pregnancy. Abnormal blood sugar levels around the time of conception and in the early weeks of pregnancy increase the risk of birth defects. The health care provider may recommend that an obese woman have a test for diabetes before pregnancy. The test involves drinking a sugary liquid, then having a blood test to measure blood sugar levels. If tests show that the woman has diabetes, she can receive treatment to get her blood sugar levels under control before she attempts to conceive. If test results are normal, her provider may ask her to repeat the test at an early prenatal visit, and again at 24 to 28 weeks of pregnancy.
At a preconception checkup, a provider can review any medications a woman takes for health conditions. The provider may change some medications to drugs that are safer for a woman to take during pregnancy. The provider also can recommend that the woman take a multivitamin containing folic acid. The March of Dimes recommends that all women of childbearing age take a multivitamin containing 400 micrograms of folic acid daily before pregnancy and in the early weeks of pregnancy to help prevent NTDs. In some cases, the provider may recommend that an obese woman take a higher amount of folic acid because of her increased risk of having a baby with an NTD.
What can an obese woman do during pregnancy to reduce her risk of complications?
It is important for all pregnant women to gain the right amount of weight to help their baby get a healthy start in life. All pregnant women should develop an individualized plan for weight gain with their health care provider. New guidelines from the IOM recommend that obese pregnant women limit their weight gain to 11 to 20 pounds during pregnancy (2). This means that they should gain 1.1 to 4.4 pounds in the first trimester and about a half-pound a week during the second and third trimesters. This weight gain allows for normal fetal growth and development and helps prevent pregnancy complications. It also helps women lose the weight they gained during pregnancy after they have the baby.
The IOM also recommends that women at a normal weight before pregnancy should gain 25 to 35 pounds during pregnancy. Women who are overweight before pregnancy should gain 15 to 25 pounds. And women who are underweight before pregnancy should gain 28 to 40 pounds (2).
An obese pregnant woman should eat healthy foods that contain plenty of fiber and complex carbohydrates (starches found in fruits, vegetables and whole grains). If possible, she should plan her diet with her provider or a nutritionist to make sure she is getting all the nutrients she and her baby need, while limiting her weight gain. With her health care provider’s OK, she should exercise on most days of the week. Exercise helps control weight gain. Brisk walking, swimming, riding a stationary bicycle or taking a pregnancy aerobics class are forms of exercise that are safe for most pregnant women.
All pregnant women should go for a prenatal checkup as soon as they think they could be pregnant. They should go to all their prenatal visits, even if they feel fine, so their health care provider can make sure everything’s OK with mom and baby.
Does weight-loss surgery reduce the risk of pregnancy complications in obese women?
More than 50,000 women a year have various types of weight-loss surgery, including gastric (stomach) banding and gastric bypass (8). These procedures usually are recommended only for individuals who are severely obese (BMI of 40 or more, or 232 pounds for a 5’4” woman) or who have a BMI of 35 or more with other complications (9). Many obese women may be able to lose weight before pregnancy with diet, exercise, behavioral changes and drug treatment.
Studies of women who have lost weight following weight-loss surgery suggest that their risk of certain pregnancy complications, including gestational diabetes and high blood pressure, are lower than those of obese women who have not had surgery (8, 9). The risk of newborn complications, including birth defects, premature birth and large size, also appears lower. Fertility also improves in many women, possibly because hormone levels tend to return to normal following weight loss.
Health care providers generally recommend that women who have had weight-loss surgery wait at least 1 year before attempting to conceive (8, 9). During that time the woman may be losing weight rapidly, which could pose a risk to an unborn baby. Some women also may need to take vitamin supplements to make sure they’re getting all the nutrients they need.
A small number of women who have had weight-loss surgery have experienced serious gastrointestinal complications, such as intestinal obstruction (blockage), during pregnancy (8, 9). Though these problems appear uncommon, a pregnant woman who has had weight-loss surgery should be checked by her weight-loss surgeon if she has abdominal pain during pregnancy (9).
Does the March of Dimes support research on obesity and pregnancy?
The March of Dimes, along with other national organizations concerned with maternal and infant health, co-sponsored the IOM study that led to new weight-gain guidelines for obese pregnant women. A current grantee is studying how maternal obesity may contribute to changes in the nutritional environment before birth, possibly increasing the likelihood of obesity and diabetes in offspring. The goal of this research is to develop treatment to help prevent these disorders, which contribute to birth defects, premature birth and other pregnancy complications. Another grantee is seeking to identify genes that help regulate fat storage and, ultimately, improve the outcomes of pregnancy by preventing obesity.