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 measurement based on height and weight — called the body mass index (BMI) — is often used to determine if a person is obese.

BMI Weight status
Below 18.5 Underweight
18.5-24.9 Normal
25.0-29.9 Overweight
30.0-34.9 Obese (Class I)
35.0-39.9 Obese (Class II)
40.0 and higher Extreme obesity (Class III)

Being obese can harm your fertility by inhibiting normal ovulation. Even in women who regularly ovulate, the greater the BMI, the longer it appears to take to become pregnant. Obesity can also affect the outcome of in vitro fertilization (IVF). As your BMI increases, so does the risk of unsuccessful IVF.

Being obese 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, often the kidneys (preeclampsia)
  • Cardiac dysfunction
  • Sleep apnea
  • A difficult vaginal delivery
  • The need for a C-section and the risk of C-section complications, such as wound infections

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

  • Being significantly larger than average (fetal macrosomia) and having more body fat than normal, which increases the risk of metabolic syndrome and childhood obesity
  • Having birth defects — and obesity makes it harder to detect these conditions with ultrasound

Your pre-pregnancy weight and BMI, as well as your health and your baby's health, all play roles 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).

For women who are extremely obese, gaining less than the recommended amount or losing weight during pregnancy might lower the risk of having a baby whose weight is greater than the 90th percentile for gestational age (large for gestational age), a condition known as fetal macrosomia. However, research suggests that losing weight or gaining too little during pregnancy also increases the risks of premature birth and having a baby whose weight is less than the 10th percentile for gestational age (small 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.

If you're obese, 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're obese, 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. Because ultrasound waves don't easily penetrate abdominal fat tissue, however, obesity during pregnancy can interfere with the effectiveness of fetal ultrasound. You might need an experienced sonographer, a repeat exam or an ultrasound that uses more advanced equipment.
  • 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.

You can limit the impact of obesity on your pregnancy and help 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 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, 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, 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.

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.

May 18, 2018