What is obesity?

When someone has more body fat than is ideal for her height and build, we say she's overweight. If she's overweight by 20 percent or more, she's considered obese.

The most common way to determine obesity is the body mass index (BMI). You can figure out your BMI by using the Centers for Disease Control and Prevention's BMI calculator or by following these steps:

  1. Multiply your weight in pounds by 703.
  2. Divide that answer by your height in inches.
  3. Divide that number again by your height in inches.

For example, a woman who weighs 140 pounds and is 5 feet 5 inches (or 65 inches) tall has a BMI of 23.3, while a woman who weighs 160 pounds and is 5 feet 5 inches has a BMI of 26.6.

In general, the federal guidelines say, a BMI of 25 to 29.9 means you're overweight and a BMI of 30 and above is defined as obese. A BMI of 18.5 to 24.9 is considered normal and healthy.

Although the BMI is a quick and easy way to measure the relationship between your weight and your height, obesity is determined by body fat, not just weight. Someone who weighs more than normal but is very muscular and has relatively little body fat might have a high BMI but is not obese. (Athletes often fall into this category.) At the other extreme, someone who is at normal weight or underweight can have excessive body fat.

What health problems are linked to obesity?

Being overweight puts you at an increased risk for many diseases and health conditions, including high blood pressure, type 2 diabetes, stroke, coronary heart disease, high blood cholesterol and triglycerides (dyslipidemia), and gallbladder disease.

Being overweight or obese can cause serious pregnancy-related problems, including labor and delivery complications, birth defects, fetal and neonatal death, and delivery of a large baby. Also, overweight pregnant women are more susceptible to certain conditions such as preeclampsia, gestational diabetes, and gestational hypertension. These risks go up as the mother's BMI increases.

While any woman of any race can be overweight, the condition is more common among African American women. Also, several studies have indicated that overweight blacks are more likely to have pregnancy complications than overweight Caucasians.

The good news is that most of these complications are manageable and, in some cases, preventable – and you may not experience any of them. You could have a perfectly healthy pregnancy and delivery even if you're overweight or obese.

That said, pregnancy is a good time to change behaviors associated with obesity to improve your long-term health and help give your new baby a healthy start in life. If you adopt a healthy diet and make physical activity a part of your daily routine, you'll set a better example for your new child.

Why is it especially important for black women to know about obesity?

The number of Americans who are obese has risen dramatically among the general U.S. population in the past 40 years, and the highest rates are among African American women. Nearly 80 percent of African American women age 20 or older are overweight or obese compared with 58 percent of white women in the same age group.

Fifteen percent of black women are obese, compared with 5 percent of white women.

Studies show that several cultural factors may contribute to the high rates of obesity among African American women. Those include unhealthy diets, not enough physical activity, and a greater acceptance of larger body types in the African American community.

Twenty-eight percent of African Americans have a poor diet, compared with 16 percent of whites, and black women report exercising less than Caucasian women.

What are the risks to my baby and me if I'm overweight or obese during pregnancy?

Being overweight or obese can lead to pregnancy complications and a difficult labor and delivery. An overweight pregnant woman is four times more likely to be hospitalized, and if her BMI is over 35, the risk is increased to six or seven times, according to Geddis Abel-Bey, an ob-gyn with a private practice in Queens.

A pregnant overweight or obese woman is also at risk for the following:

  • Preeclampsia This serious disorder occurs when a pregnant woman has high blood pressure and protein in her urine after 20 weeks of pregnancy. Untreated preeclampsia can cause serious to fatal complications in both mother and baby.
  • Preeclampsia affects 3 to 8 percent of pregnant women, and it's more common among African Americans. African Americans often develop the condition earlier and in a more severe form than Caucasians.
  • Studies have shown that about 9 to 12 percent of overweight and obese women are diagnosed with preeclampsia, while 4 to 5 percent of women with a BMI in the 19 to 25 range develop the condition.
  • Gestational hypertension If you develop high blood pressure after 20 weeks of pregnancy but don't have protein in your urine, you'll be diagnosed with gestational hypertension, sometimes called pregnancy-induced hypertension. If the hypertension is severe, it can cause intrauterine growth restriction and low birth weight.
  • Several studies have shown that roughly 10 percent of obese women (BMI of 30 or above) will have gestational hypertension, versus around 4 percent of women with a BMI of 19 to 25.
  • Gestational diabetes This type of diabetes develops during pregnancy. Like other forms of diabetes, gestational diabetes affects the way your body uses sugar (glucose) – your body's main source of fuel.
  • Gestational diabetes can cause high blood sugar levels that are unlikely to lead to problems for you, but if left untreated, the baby faces an increased risk of being born too large (9 pounds 15 ounces or more). The chances for birth defects and stillbirth also go up.
  • About 6 percent of overweight women and 9 percent of obese women develop gestational diabetes, while 2 percent of women with a BMI of 19 to 24 develop it.
  • You can manage gestational diabetes by gaining only the recommended weight during pregnancy (see below), eating healthy foods, exercising regularly, and, if necessary, taking medication.
  • Preterm birth If you deliver your baby before 37 weeks, your baby is considered premature and is at an increased risk for health complications. About 12 percent of babies in the United States are born prematurely, and the risk is greater if the mother is overweight. One study found that among obese women, the risk for preterm birth is highest among blacks, while whites and Hispanics both had significantly lower levels of risk.
  • Longer labor Overweight women progress through labor more slowly than women at a healthy weight, some studies have found. They're also more likely to have irregular contractions during the first stage of labor and more likely to receive oxytocin to induce labor.
  • Hard-to-place epidural There's no evidence suggesting that epidurals don't work as well specifically in larger women. However it can sometimes be more difficult to get the medication where it needs to go, which can affect your pain relief.
  • One study stated that epidural pain relief in labor is more often "ineffective" in obese women, due solely to whether the anesthesiologist managed to get the needle into the spine properly. It can be more difficult for an anesthesiologist to place the epidural if he can't feel the spine as easily under extra fatty tissue, but once the needle is in – and there are various needle lengths to suit all sizes of patients – and the appropriate medicine has been given, it should work just as well as it would on a smaller woman.
  • C-section Overweight women are twice as likely to require a surgical delivery as women with a normal BMI. When an overweight woman has a c-section, complications related to anesthesia, infec­tions at the incision site, and life-threatening pulmonary embolism (a blockage of an artery in the lungs by fat, air, tumor tissue, or blood clot) are gen­erally more common.

The baby of an obese woman is at risk for the following complications:

  • Birth defects Overweight women are more likely to have a baby with birth defects, especially neural tube defects (NTDs). They're also 30 to 40 percent more likely to deliver a baby with major birth defects that affect the brain, heart, and digestive system.
  • Folic acid supplements, which are usually effective in preventing NTDs and other birth defects, may not be as protective in overweight women, according to some studies.
  • Macrosomia Babies of obese women are more likely to weigh 9 pounds or more, and when the baby is more than 9 pounds 15 ounces, it's a condition known as macrosomia. Women who deliver large babies are more susceptible to injuries during vaginal delivery. Also, women who previously delivered a macrosomic baby are five to ten times more likely than women without such a history to deliver a large baby the next time they're pregnant, especially if they remain obese.
  • Childhood obesity The effect of your weight on your child doesn't end at birth. In a study of African American children, being born to an overweight mother increased a child's risk for being overweight later in life. This is mainly because the behaviors associated with being overweight are learned at home.
  • Childhood obesity is a growing problem in the African American community. Studies show that almost 36 percent of black children between the ages of 6 and 11 are overweight, and more than 19 percent are considered obese. Pregnancy is a good time to change your eating and exercise behaviors and stop the generational effect.
  • Also, there is evidence suggesting that obesity in pregnant women creates an unhealthy fetal environment that increases the baby's risk for obesity later in life. It's as if the thermostat for body fat percentage is set in utero.

For more information on the risks associated with obesity, read Baby Center's article Plus-size and pregnant: Understanding and managing health risks.

How is obesity managed during pregnancy?

Pregnancy and obesity can be a challenging combination. But a healthy pregnancy is possible by properly managing weight gain, taking good care of yourself, and working closely with your healthcare provider. Here are some important tips:

  • See a healthcare provider before pregnancy. If you're overweight, meet with a doctor or midwife for a physical and preconception counseling before you get pregnant if you possibly can. Early visits give your healthcare provider a chance to educate, screen for risks, and evaluate any medications you're taking. Also, your provider will probably suggest that you try to reach a more healthy weight several months before conceiving.
  • Watch your weight, but don't diet. Once you're pregnant, your healthcare provider will probably discourage you from going on a weight-loss diet. Restricting your food intake is potentially hazardous to you and your developing baby. Your provider may suggest the same 2,000-calorie-per-day diet he would recommend to any other woman.
  • That said, in the first trimester, it's common to lose weight as the result of morning sickness: The nausea can diminish your appetite, and the vomiting can cause you to miss out on calories. But don't worry, your baby will still get all the necessary calories. Overweight women have an extra reserve of calories in stored fat, so as your baby grows, it's okay for you to maintain or even lose a little weight in the first trimester.
  • Eat healthy. Ask your healthcare provider about seeing a nutritionist who can help you adopt healthier eating habits, direct you to foods that will satisfy your hunger, and suggest nutrient-packed meals that will help your baby grow.
  • "An overweight woman has to focus on what they call a nutrient-dense diet. Foods that are nutrient dense, such as whole grains, beans, vegetables, low-fat dairy, and lean protein, provide a high nutrient-to-calorie ratio. Foods with low nutrient density have a lot of fat and sugar but basically no other nutrients," says ob-gyn Abel-Bey.
  • You can use our handy pregnancy food diary to make sure you're getting enough nutrients and drinking plenty of water every day.
  • Exercise: Unless there's a medical reason not to exercise, moderate exercise of 30 minutes or more several days a week is recommended. Ideally, start exercising before you become pregnant. Studies show that physical activity in morbidly obese women (BMI greater than 35) can help reduce the risk of developing conditions in pregnancy such as gestational diabetes.
  • Be sure to consult your caregiver before starting any sort of exercise program. And stop exercising immediately if you have any of these symptoms: vaginal bleeding, shortness of breath before exercise, dizziness, headache, chest pain, muscle weakness, calf pain or swelling, preterm contractions, leaking of amniotic fluid, or your baby isn't moving as much.
  • For more information, read our article on pregnancy exercise for beginners.
  • Attend prenatal appointments. Your healthcare provider will monitor you and your baby closely during pregnancy by checking your blood pressure and discussing recommended weight gain, and using ultrasounds and fetal heart monitoring to check on your baby. You may also be screened twice for gestational diabetes, first at the beginning of your pregnancy and again in your second or third trimester.
  • Get more tips from our article on how to manage your weight during pregnancy.

If I'm overweight exactly how much weight should I gain during pregnancy?

It depends on how much you weighed before you conceived and how appropriate that weight is for your height. As a comparison, experts advise women with a healthy BMI – 18.5 to 24.9 – to gain between 25 and 35 pounds.

If you're overweight for your height (a BMI of 25 to 29.9), you should gain between 15 and 25 pounds by the end of your pregnancy, at a rate of approximately 2 to 3 pounds a month, primarily in your second and third trimesters. It's normal not to gain any weight at all during the first trimester, when morning sickness is at its worst.

Obese women (those with a BMI of 30 or higher) should gain between 11 and 20 pounds.

If you're having twins, you should gain 31 to 50 pounds if you're overweight, and 25 to 42 pounds if you're obese.

Use our pregnancy weight gain estimator to get an idea of how much you should gain (based on your height and pre-pregnancy weight) and to see how the pounds are distributed.