Concerned about pregnancy and obesity? Understand the risks of obesity during pregnancy — plus steps to promote a healthy pregnancy. By Mayo Clinic Staff

Being obese 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.

Obesity is defined as having an excessive amount of body fat. A formula based on height and weight — called the body mass index (BMI) — is often used to determine if a person is obese.

BMIWeight status
Below 18.5 Underweight
18.5-24.9 Normal
25-29.9 Overweight
30 and higher Obese
40 and higher Extreme obesity

Being obese can harm your fertility by inhibiting normal ovulation. Obesity can also affect the outcome of in vitro fertilization (IVF). As a woman's BMI increases, so does the risk of unsuccessful IVF.

Being obese during pregnancy increases the risk of various pregnancy complications, including:

  • Gestational diabetes. Women who are obese are more likely to have diabetes that develops during pregnancy (gestational diabetes) than are women who have a normal weight.
  • Preeclampsia. Women who are obese are at increased risk of developing high blood pressure and protein in the urine after 20 weeks of pregnancy (preeclampsia).
  • Infection. Women who are obese during pregnancy are at increased risk of urinary tract infections. Obesity also increases the risk of postpartum infection, whether the baby is delivered vaginally or by C-section.
  • Thrombosis. Women who are obese during pregnancy are at increased risk of a serious condition in which a blood clot forms inside a blood vessel (thrombosis).
  • Obstructive sleep apnea. Women who are obese during pregnancy might be at increased risk of a potentially serious sleep disorder in which breathing repeatedly stops and starts (obstructive sleep apnea). Pregnancy might also worsen existing obstructive sleep apnea.
  • Overdue pregnancy. Obesity increases the risk that pregnancy will continue beyond the expected due date.
  • Labor problems. Labor induction is more common in women who are obese. Obesity can also interfere with the use of certain types of pain medication, such as an epidural block.
  • C-section. Obesity during pregnancy increases the likelihood of elective and emergency C-sections. Obesity also increases the risk of C-section complications, such as delayed healing and wound infections. Women who are obese are also less likely to have a successful vaginal delivery after a C-section (VBAC).
  • Pregnancy loss. Obesity increases the risk of miscarriage and stillbirth.

Obesity during pregnancy can cause various health problems for a baby, including:

  • Macrosomia. Women who are obese are at increased risk of delivering an infant who is significantly larger than average (macrosomia) and has more body fat than normal. Research suggests that as birth weight increases, so does the risk of childhood obesity.
  • Chronic conditions. Being obese during pregnancy might increase the risk that your baby will develop heart disease or diabetes as an adult.
  • Birth defects. Research suggests that obesity during pregnancy slightly increases the risk of having a baby who's born with a birth defect, such as a problem with the heart or a condition affecting the brain or spinal cord (neural tube defect).

Your pre-pregnancy weight and body mass index (BMI), as well as your health and your baby's health, all play a role in determining how much weight you need to gain during pregnancy. Work with your health care provider to determine what's best in your case and to manage your weight throughout pregnancy.

Start by considering these general guidelines for pregnancy weight gain and obesity:

  • Single pregnancy. If you're obese and carrying one baby, the recommended weight gain is 11 to 20 pounds (about 5 to 9 kilograms).
  • Multiple pregnancy. If you're obese and carrying twins or multiples, the recommended weight gain is 25 to 42 pounds (about 11 to 19 kilograms).

Still, some research suggests that women who are obese can safely gain less weight than the guidelines recommend.

Rather than gaining or losing a specific amount of weight during pregnancy, your health care provider might encourage you to focus on avoiding excessive weight gain during pregnancy.

If you're obese, your health care provider will closely monitor your pregnancy. Depending on the circumstances, your health care provider 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're obese and pregnant, your health care provider might recommend the screening test earlier in your pregnancy — perhaps even 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.
  • Delayed fetal ultrasound. Fetal ultrasound is an imaging technique that uses high-frequency sound waves to produce images of the baby in your uterus. Fetal ultrasound is typically done between weeks 18 and 20 of pregnancy to evaluate a baby's growth and development. Since ultrasound waves don't easily penetrate abdominal fat tissue, however, obesity during pregnancy can interfere with the effectiveness of fetal ultrasound. Ultrasound results might be more detailed if the test is done a few weeks later, such as between weeks 20 and 22 of pregnancy.
  • Fetal echocardiography. Your health care provider might recommend a fetal ultrasound that provides a detailed picture of your baby's heart (fetal echocardiography) between weeks 20 and 22 of pregnancy. This test is used to rule out or confirm a congenital heart defect.
  • Frequent prenatal visits. As your pregnancy progresses, your health care provider might recommend more frequent prenatal visits to monitor your health and your baby's health. Regular fetal ultrasounds might be recommended as well. The ultrasounds can help your health care provider evaluate your baby's growth and plan for your delivery.

You can limit the impact of obesity on your pregnancy and ensure your health and your baby's health. For example:

  • Schedule a preconception appointment. If you're obese 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 or an obesity specialist — who can help you make changes in your lifestyle and 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 might 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, calcium, iron and other essential nutrients. A daily prenatal vitamin can help fill any gaps. Consult your health care provider if you have special nutritional needs due to a health condition, such as diabetes.
  • Be physically active. Consult your health care provider about safe ways to stay physically active during your pregnancy.
  • 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.

Obesity during pregnancy can increase the risk of complications for you and your baby. To ease your anxiety, work closely with your health care provider. He or she can help you avoid excessive weight gain, manage any medical conditions, and monitor your baby's growth and development.

Dec. 28, 2012