Having a high body mass index (BMI) during pregnancy can have a major impact on your health and your baby's health. Find out about the possible complications, recommendations for weight gain and what you can do to promote a healthy pregnancy.
What's considered obese?
Obesity is diagnosed when your BMI is 30 or higher. To determine your body mass index, divide your weight in pounds by your height in inches squared and multiply by 703. Or divide your weight in kilograms by your height in meters squared.
BMI Weight status
Below 18.5 Underweight
18.5-24.9 Normal
25.0-29.9 Overweight
30.0 and higher Obesity
Could having a high BMI affect my ability to get pregnant?
Having a high BMI can harm your fertility by inhibiting normal ovulation. Even in women who regularly ovulate, the higher the BMI, the longer it appears to take to become pregnant. Some research also suggests that as your BMI increases, so does the risk of unsuccessful in vitro fertilization (IVF).
How might a high BMI affect my pregnancy?
Having a high BMI during pregnancy increases the risk of various pregnancy complications, including:
- The risk of miscarriage, stillbirth and recurrent miscarriage
- Gestational diabetes
- A pregnancy complication characterized by high blood pressure and signs of damage to another organ system, most often the liver and kidneys (preeclampsia)
- Cardiac dysfunction
- Sleep apnea
- The need for a C-section and the risk of C-section complications, such as wound infections
How could obesity affect my baby?
Having a high BMI during pregnancy has been linked to an increased risk of various health problems for a baby, including:
- Birth defects
- Being significantly larger than average (fetal macrosomia)
- Impaired growth
- Childhood asthma
- Childhood obesity
However, other factors also might play a role in these outcomes.
How much weight should I gain during pregnancy?
Your pre-pregnancy weight and BMI is important to consider when determining how much weight you need to gain during pregnancy. Work with your health care provider to find out what's best for you and to manage your weight throughout pregnancy.
Start by considering these guidelines for pregnancy weight gain and obesity:
- Single pregnancy. If you have a BMI of 30 or higher and are carrying one baby, the recommended weight gain is 11 to 20 pounds (about 5 to 9 kilograms).
- Multiple pregnancy. If you have a BMI of 30 or higher and are carrying twins or multiples, the recommended weight gain is 25 to 42 pounds (about 11 to 19 kilograms).
For women who have a BMI of 40 or higher, gaining less than the recommended amount or losing weight during pregnancy might lower the risk of a C-section or having a baby significantly larger than average. However, this approach also might increase the risk of having a baby whose weight is smaller than expected for gestational age.
Rather than recommending that you gain a specific amount of weight during pregnancy, your health care provider might encourage you to focus on avoiding excessive weight gain during pregnancy.
Will I need specialized care during pregnancy?
If you have a BMI of 30 or higher, your health care provider will closely monitor your pregnancy. He or she might recommend:
- Early testing for gestational diabetes. For women at average risk of gestational diabetes, a screening test called the glucose challenge test is often done between weeks 24 and 28 of pregnancy. If you have a BMI of 30 or higher, your health care provider might recommend the screening test at your first prenatal visit. If your test results are normal, you'll likely repeat the screening test between weeks 24 and 28 of pregnancy. If the results are abnormal, you'll need further testing. Your health care provider can advise you on blood sugar monitoring and control.
- Changes to your fetal ultrasound. A standard fetal ultrasound is typically done between weeks 18 and 20 of pregnancy to evaluate a baby's anatomy. But ultrasound waves don't easily penetrate abdominal fat tissue. This can interfere with the effectiveness of fetal ultrasound. Talk to your health care provider about the best approach for getting an accurate ultrasound.
- Screening for obstructive sleep apnea. This is a potentially serious sleep disorder that causes breathing to repeatedly stop and start during sleep. Women who have obstructive sleep apnea during pregnancy are at increased risk of preeclampsia and other complications. You'll likely be screened at your first prenatal visit. If obstructive sleep apnea is suspected, your health care provider may refer you to a sleep medicine specialist for evaluation and possible treatment.
What steps can I take to promote a healthy pregnancy?
You can limit the impact of having a high BMI and help ensure your health and your baby's health. For example:
- Schedule a preconception appointment. If you have a BMI of 30 or higher and you're considering getting pregnant, talk to your health care provider. He or she might recommend a daily prenatal vitamin and refer you to other health care providers — such as a registered dietitian — who can help you reach a healthy weight before pregnancy.
- Seek regular prenatal care. Prenatal visits can help your health care provider monitor your health and your baby's health. Tell your health care provider about any medical conditions you have — such as diabetes, high blood pressure or sleep apnea — and discuss what you can do to manage them.
- Eat a healthy diet. Work with your health care provider or a registered dietitian to maintain a healthy diet and avoid excessive weight gain. Keep in mind that during pregnancy, you'll need more folic acid, protein, calcium, iron and other essential nutrients.
- Be physically active. Consult your health care provider about safe ways to stay physically active during your pregnancy, such as walking, swimming or doing low-impact aerobics.
- Avoid risky substances. If you smoke, ask your health care provider to help you quit. Alcohol and illicit drugs are off-limits, too. Get your health care provider's OK before you start or stop taking any medications or supplements.
Having a BMI of 30 or higher during pregnancy can increase the risk of complications for you and your baby. Working with your health care provider can help you manage your risks and promote a healthy pregnancy.
