Obesity and Pregnancy
Frequently Asked Questions Expand All
Being overweight is defined as having a body mass index (BMI) of 25 to 29.9. Obesity is defined as having a BMI of 30 or greater. Within the general category of obesity, there are three levels that reflect the increasing health risks that go along with increasing BMI:
Obesity category I—BMI of 30 to 34.9
Obesity category II—BMI of 35 to 39.9
Obesity category III—BMI of 40 or greater
You can find out your BMI by using an online BMI calculator.
Obesity during pregnancy puts you at risk of several serious health problems:
Preeclampsia—Preeclampsia is a serious form of gestational hypertension that usually happens in the second half of pregnancy or soon after childbirth. This condition can cause the woman's kidneys and liver to fail. In rare cases, seizures, heart attack, and stroke can happen. Other risks include problems with the placenta and growth problems for the fetus.
Gestational diabetes—High levels of glucose (blood sugar) during pregnancy increase the risk of having a very large baby. This also increases the chance of cesarean birth. Women who have had gestational diabetes have a higher risk of diabetes mellitus in the future. So do their children.
Obstructive sleep apnea—Sleep apnea is a condition in which a person stops breathing for short periods during sleep. During pregnancy, sleep apnea can cause fatigue and increase the risk of high blood pressure, preeclampsia, and heart and lung problems.
Obesity increases the risk of the following problems during pregnancy:
Problems with diagnostic tests—Having too much body fat can make it difficult to see certain problems with the fetus’s anatomy on an ultrasound exam. Checking the fetus’s heart rate during labor also may be more difficult if you are obese.
Macrosomia—In this condition, the fetus is larger than normal. This can increase the risk of injury during birth. For example, the fetus’s shoulder can get stuck after the head is delivered. Macrosomia also increases the risk of cesarean birth. Infants born with too much body fat have a greater chance of being obese later in life.
Preterm birth—Problems associated with a woman’s obesity, such as preeclampsia, may lead to a medically indicated preterm birth. This means that the baby is delivered early for a medical reason. Preterm babies are not as fully developed as babies who are born after 39 weeks of pregnancy. As a result, preterm babies have an increased risk of short-term and long-term health problems.
Stillbirth—The higher the woman’s BMI, the greater the risk of stillbirth.
Losing weight before you get pregnant is the best way to decrease the risk of problems caused by obesity. Losing even a small amount of weight can improve your overall health and pave the way for a healthier pregnancy.
To lose weight, you need to use up more calories than you take in. You can do this by getting regular exercise and eating healthy foods. Your obstetrician–gynecologist (ob-gyn) may refer you to a nutritionist to help you plan a healthy diet. Also, the MyPlate website from the U.S. Department of Agriculture has a special section for women who are pregnant or breastfeeding.
Increasing your physical activity is important if you want to lose weight. Aim to be moderately active (for example, biking, brisk walking, and general gardening) for 60 minutes or vigorously active (jogging, swimming laps, or doing heavy yard work) for 30 minutes on most days of the week. You do not have to do this amount all at once. For instance, you can exercise for 20 minutes three times a day.
If you have tried to lose weight through diet changes and exercise and you still have a BMI of 30 or greater or a BMI of at least 27 with certain medical conditions, such as diabetes or heart disease, weight-loss medications may be suggested. These medications should not be taken if you are trying to get pregnant or are already pregnant.
Bariatric surgery may be an option for people who are very obese or who have major health problems caused by obesity. If you have weight loss surgery, you should delay getting pregnant for 12 to 24 months after surgery, when you will have the most rapid weight loss.
If you have had fertility problems, they may resolve on their own as you rapidly lose the excess weight. It is important to be aware of this because the increase in fertility can lead to an unplanned pregnancy.
Some types of bariatric surgery may affect how the body absorbs medications taken by mouth, including birth control pills. You may need to switch to another form of birth control.
Despite the risks, you can have a healthy pregnancy if you are obese. It takes careful management of your weight, attention to diet and exercise, regular prenatal care to monitor for complications, and special considerations for your labor and delivery.
Finding a balance between eating healthy foods and staying at a healthy weight is important for your health and your fetus's health. In the second and third trimesters, a pregnant woman needs an average of 300 extra calories a day—about the amount of calories in a glass of skim milk and half of a sandwich. You can get help with planning a healthy diet by talking to a nutrition counselor. Help also can be found at the MyPlate website.
If you have never exercised before, pregnancy is a great time to start. Discuss your exercise plan with your ob-gyn to make sure it is safe. Begin with as little as 5 minutes of exercise a day and add 5 minutes each week. Your goal is to stay active for 30 minutes on most—preferably all—days of the week.
Walking is a good choice if you are new to exercise. Swimming is another good exercise for pregnant women. The water supports your weight so you can avoid injury and muscle strain. It also helps you stay cool. Read Exercise During Pregnancy for more advice.
Your weight should be tracked at each prenatal visit. The growth of your fetus also will be checked. If you are gaining less than the recommended guidelines, and if your fetus is growing well, you do not have to increase your weight gain to catch up to the guidelines. If your fetus is not growing well, changes may need to be made to your diet and exercise plan.
Women who are overweight and obese have longer labors than women of normal weight. It can be harder to monitor the fetus during labor. For these reasons, obesity during pregnancy increases the likelihood of having a cesarean birth. If a cesarean birth is needed, the risks of infection, bleeding, and other complications are greater for a woman who is obese than for a woman of normal weight.
Once you are home with your new baby, stick to your healthy eating and exercise habits to reach a normal weight. Breastfeeding is recommended for the first year of a baby’s life. Not only is breastfeeding the best way to feed your baby, it also may help with postpartum weight loss. Overall, women who breastfeed their babies for at least a few months tend to lose pregnancy weight faster than women who do not breastfeed.
Bariatric Surgery: Surgical procedures that cause weight loss. These procedures are used to treat obesity.
Birth Defects: Physical problems that are present at birth.
Body Mass Index (BMI): A number calculated from height and weight. BMI is used to determine whether a person is underweight, normal weight, overweight, or obese.
Calories: Units of heat used to express the fuel or energy value of food.
Cesarean Birth: Birth of a fetus from the uterus through an incision (cut) made in the woman’s abdomen.
Complications: Diseases or conditions that happen as a result of another disease or condition. An example is pneumonia that occurs as a result of the flu. A complication also can occur as a result of a condition, such as pregnancy. An example of a pregnancy complication is preterm labor.
Diabetes Mellitus: A condition in which the levels of sugar in the blood are too high.
Fetus: The stage of human development beyond 8 completed weeks after fertilization.
Gestational Diabetes: Diabetes that starts during pregnancy.
Gestational Hypertension: High blood pressure that is diagnosed after 20 weeks of pregnancy.
Glucose: A sugar in the blood that is the body’s main source of fuel.
High Blood Pressure: Blood pressure above the normal level. Also called hypertension.
Kidneys: Organs that filter the blood to remove waste that becomes urine.
Macrosomia: A condition in which a fetus grows more than expected, often weighing more than 8 pounds and 13 ounces (4,000 grams).
Neural Tube Defects: Birth defects that result from a problem in development of the brain, spinal cord, or their coverings.
Obesity: A condition characterized by excessive body fat.
Obstetrician–Gynecologist (Ob-Gyn): A doctor with special training and education in women’s health.
Obstructive Sleep Apnea: A serious sleep disorder that causes a person to have brief pauses in breathing during sleep.
Placenta: An organ that provides nutrients to and takes waste away from the fetus.
Preeclampsia: A disorder that can occur during pregnancy or after childbirth in which there is high blood pressure and other signs of organ injury. These signs include an abnormal amount of protein in the urine, a low number of platelets, abnormal kidney or liver function, pain over the upper abdomen, fluid in the lungs, or a severe headache or changes in vision.
Preterm: Less than 37 weeks of pregnancy.
Stillbirth: Birth of a dead fetus.
Stroke: A sudden interruption of blood flow to all or part of the brain, caused by blockage or bursting of a blood vessel in the brain. A stroke often results in loss of consciousness and temporary or permanent paralysis.
Trimesters: The 3-month times in pregnancy. They can be first, second, or third.
Ultrasound Exam: A test in which sound waves are used to examine inner parts of the body. During pregnancy, ultrasound can be used to check the fetus.
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Last updated: May 2021
Last reviewed: December 2020
Copyright 2021 by the American College of Obstetricians and Gynecologists. All rights reserved. Read copyright and permissions information.
This information is designed as an educational aid for the public. It offers current information and opinions related to women's health. It is not intended as a statement of the standard of care. It does not explain all of the proper treatments or methods of care. It is not a substitute for the advice of a physician. Read ACOG’s complete disclaimer.
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