Women's Healthcare Topics

How Does Obesity Affect Pregnancy?

Reviewed by James Brann, M.D.

What is Considered Obese

If you’re obese when you get pregnant, you’re at increased risk of certain problems, as is your unborn child. Before explaining those risks, though, first you need to understand what’s considered obese.

Your body mass index, or BMI, comes from a calculation of your weight and height. It’s used to find out whether you’re actually underweight, of normal weight, or obese. There are several BMI calculators online to help you figure it out. If your BMI ranges between 25-29.9, you are considered overweight. If your BMI is at 30 or more, you’re considered obese.

Obesity risks during pregnancy for baby

If you’re obese, your baby is at a higher risk of certain things. They include:

  • Ultrasound testing trouble - Having too much extra body weight may cause your nurse or doctor difficulty in spotting areas of concern with your child during an ultrasound.

  • Birth defects - Children with obese birth mothers have a higher risk of birth defects including neural tube defects and heart defects.

  • Early delivery (preterm birth) - Due to problems connected to a mother’s obesity, it may be necessary to deliver her child early. Babies who are preterm are at a higher risk of certain health problems including eating trouble, breathing trouble, as well as learning and developmental problems later on.

  • Larger birth weight (macrosomia) - A larger baby may have a higher risk of being injured during delivery. This may lead to the need for a cesarean delivery.

  • Stillbirth - This risk goes up with a higher maternal BMI.

Obesity risks during pregnancy for mom

Along with your baby, if you’re obese and pregnant you are additionally at an increase risk of some health problems. They may include:

  • Preeclampsia - This illness is dangerous for both a mother and her child. With preeclampsia, your liver and kidneys may stop working. Stroke may occur during rare cases. In extremely severe cases, your life, and your child’s life, is at risk.

  • High blood pressure - When high blood pressure begins after the first half of your pregnancy, it’s called gestational hypertension. This may lead to some dangerous complications.

  • Gestational diabetes - If your blood glucose, or sugar level, is too high during pregnancy, you’re at a higher risk of delivering a larger baby and needing a cesarean delivery. If you’ve had gestational diabetes, you’re at an increased risk of diabetes later in life, as are your kids.

Although there are risks, an obese woman can still deliver a healthy baby with a safe pregnancy. You’ll need to get with your doctor, though, to make sure you’re getting plenty of exercise, plus you’re monitoring your weight. You also want to ensure you’re staying as healthy as possible, and making all of your regular prenatal care visits.

You’ll want to talk to your nurse or doctor during your first prenatal appointment about how much weight you should gain. The following is a guideline of healthy weight ranges based on your pre-pregnancy weight and your BMI:

Pregnancy Health Section

Learn the risks if your are obese when you get pregnant.

Weight gain guidelines

  • Normal weight before pregnancy - 18.5-24.9 BMI - - - 25-35 total lbs gained

  • Overweight before pregnancy - 25-29.9 BMI - - - 15-25 total lbs gained

  • Obese before pregnancy - 30 or more BMI - - - 11-20 total lbs gained

Whether you are obese, or not, you don’t want to try to lose weight during a pregnancy. An obese woman may gain less weight, though, then what the guidelines suggest. As long as your baby is growing and healthy, if you’re obese and gain less than the guidelines suggest, it may mean there’s less of a risk of delivering a large baby, or needing a cesarean delivery.

If you’ve never exercised before, you don’t want to start exercising at too high of a level in the beginning. Start with five minutes a day, and then add on another five minutes of exercise on a weekly basis. You should work up to a goal of 30-minutes of activity every day. If you’re new to exercising, walking is a good thing to do. Easy on the joints, walking briskly can give you a total body workout. Another good exercise if you’re pregnant is swimming.

Vaginal delivery

The ideal way to deliver your child is vaginally. A vaginal delivery is less likely if you’re obese, though. During labor, it may be more difficult to monitor your child. There may also be difficulties during your labor and delivery if you have a very large baby. This is why being obese during pregnancy leads to a higher risk of needing a cesarean delivery.

Cesarean delivery

A cesarean delivery is even more risky for an obese woman than for a normal weight woman. The operation may take longer, and with a lengthy operation comes a higher risk of complications including bleeding. There are other risks too, including:

  • Anesthesia problems

  • Poor wound healing

  • Developing infections

  • Deep vein thrombosis (DVT)

Gestational diabetes

Being overweight or obese puts you at an increased risk of gestational diabetes over normal weight women. For this reason, your doctor may want to test you for gestational diabetes during your first trimester. You may also have to repeat the test later on.

If you do have gestational diabetes while pregnant, you’ll need to then follow-up with your doctor to retest your glucose level about six to 12 weeks post-delivery. If the test comes back normal, you’ll then likely be retested every three years for diabetes.

Losing weight after pregnancy

The best course of action is to lose the extra weight before you get pregnant, or before you get pregnant again. This may help prevent obesity-related problems during pregnancy. Especially if you developed complications in a previous pregnancy, you’ll need to lose weight before your next pregnancy.

You’ll want to do this by continuing with exercise and healthy eating. Breastfeeding may help you lose weight postpartum, as well as be beneficial to your baby. Breastfeeding moms who keep it up for at least several months are more likely to take the pregnancy weight off quicker than women who don’t breastfeed are.

To take off the weight, and keep it off, it takes most people about 60-90 minutes of moderate intensity activity almost every day. This means yard work, brisk walking or even biking.

Losing weight with medications

If you’ve tried dieting and exercise to lose weight, and your BMI is still above 30, or 27 and above with certain medical conditions like heart disease or diabetes, your doctor may talk to you about using medications for weight loss. You don’t want to take these types of medications if you become pregnant, though.

Losing weight with surgery

If you find exercise and dieting doesn’t seem to work, and neither do medications, surgery could be an option. If you’re extremely obese, you may consider bariatric surgery. This means people with a BMI of at least 40, or those between 35-39 BMI who suffer from major obesity-related health problems.

If you do undergo weight-loss surgery, you’ll want to wait between 12 and 24 months post-surgery before getting pregnant. Certain types of weight-loss surgery impact how you absorb oral medications, birth control pills included. In this case, you may want to consider switching to another type of birth control.


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