Plus size pregnancy: What to know about your health

What is considered a plus size pregnancy?

You're considered overweight if your pre-pregnancy body mass index (BMI) is between 25 and 29.9 and obese if your BMI is 30 or higher. It's healthy to have a BMI between 18.5 and 24.9. (Not sure what yours is? Find out your BMI.Opens a new window)

Keep in mind that BMI is only a rough estimate of body fat based on your height and weight: It doesn't take genetics, race, or age into consideration, and it isn't a perfect tool for assessing overall fitness. Nevertheless, researchers have consistently found that as BMI increases, so does the risk of many pregnancy and labor complications.

Although having a BMI between 18.5 and 24.9 is considered normal, it isn't all that typical: About half of first-time mothers in the United States are overweight when they become pregnant, and about half of first-time mothers also gain too much weight during pregnancy.

How important is your weight during pregnancy?

What you weigh when you become pregnant – and how much weight you gain during pregnancy – can affect your pregnancy and your baby. Gaining too little weight can put women at risk of premature delivery and having a baby with low birthweight, while gaining too much can put you at higher risk for other pregnancy complications (see below).

Starting pregnancy at a healthy weight is ideal, but keep in mind that most women who fall outside the weight recommendations still have normal pregnancies and healthy babies. Many of the conditions and complications linked to an overweight pregnancy are manageable – and in some cases preventable.

Health conditions associated with plus size pregnancies

If you're carrying extra weight going into pregnancy, you’re more susceptible to some pregnancy complications. Understanding your risk factors will help you do everything you can to enjoy a safe and healthy plus-size pregnancy.

Gestational diabetes

This condition causes elevated blood sugar during pregnancy. Your healthcare provider will evaluate your blood sugar during glucose screening and tolerance tests, which are usually done between 24 and 28 weeks of pregnancy. (They may be done earlier if you're overweight at conception or have other risk factors.)

Nearly 5 percent of pregnant women develop gestational diabetes, and the risk increases along with BMI: Overweight women are twice as likely to have gestational diabetes, and obese women are four to eight times as likely to have it. Almost half of gestational diabetes cases are attributable to being overweight or obese.

Uncontrolled gestational diabetes, or high blood sugar levels, can increase the risk of:

• Hypoglycemia (low blood sugar), jaundice, and breathing problems in your baby after birth
• Having a large baby, increasing the risk of injury and shoulder dystocia – a rare but serious situation in which the baby becomes stuck behind the mother's pubic bone during delivery
• Developing diabetes yourself in the future
• Having a child who develops type 2 diabetes and/or obesity
• Cesarean birth

Preeclampsia

Also known as toxemia, preeclampsia is a serious condition that's diagnosed after 20 weeks of pregnancy (or during labor or postpartum) if you have high blood pressure along with at least one other symptom. These can include protein in your urine, liver or kidney abnormalities, persistent headaches, or vision changes.

About 6 to 12 percent of overweight and obese women will be diagnosed with preeclampsia, while about 4 percent of women with a BMI in the normal range will be diagnosed.

Preeclampsia affects your blood vessels, which raises your blood pressure and affects organ systems throughout your body. Preeclampsia can range from mild to severe and progress slowly or rapidly. In severe cases, it can cause growth problems for your baby and the following for you and your pregnancy:

• Kidney and/or liver problems
• Low platelets and bleeding problems
• Low amniotic fluid
• Placental abruption, a serious condition in which the placenta separates partially or completely from your uterus before your baby is born
• Eclampsia (seizures)
• Heart attack
• Stroke

Gestational hypertension

If you develop high blood pressure (a reading of 140 over 90 or higher – even if only one of the numbers is elevated) after 20 weeks of pregnancy but don't have any evidence of preeclampsia, you'll be diagnosed with gestational hypertension, sometimes called pregnancy-induced hypertension. Roughly 10 percent of obese women have gestational hypertension, versus around 4 percent of women with normal BMI.

If you had high blood pressure before pregnancy, or are diagnosed with it before 20 weeks of pregnancy, that's called chronic hypertension. Chronic hypertension is a heart risk, but gestational hypertension is usually mild and probably won't cause any noticeable problems for you or your baby. However, it does put you at higher risk for:

• Preeclampsia
• Intrauterine growth restriction, also called fetal growth restriction
• Preterm birth
• Placental abruption
• Stillbirth

Obstructive sleep apnea

This means that you stop breathing for short periods during sleep, temporarily decreasing the amount of oxygen in your blood. Being overweight or obese puts you at higher risk of sleep apnea. In fact, the heavier you are to begin with and the more weight you gain during pregnancy, the more likely you are to have trouble breathing during sleep.

Sleep apnea during pregnancy can lead to fatigue and increase the risk of:

• High blood pressure
• Preeclampsia
• Heart and lung problems

Longer labor

Several studies have found that higher BMI is linked to longer active labor. In one study of over 5,000 women, the first stage of labor – and specifically until 6 cm dilation – lasted more than an hour longer than it did for normal-weight women. For women with BMIs greater than 40, the first stage of labor was almost two hours longer than in normal-weight women. But this doesn't necessarily mean you'll be in labor longer.

Talk with your doctor or midwife about how the difference in the progression of labor for plus-size women differs from that of women in normal weight ranges. Make sure that any decision made about having a cesarean delivery takes into account different expectations for the labor progression expected for your weight.  (It can be harder to monitor the baby of a plus-sized woman during labor, too.)

Labor complications

A study of over 250,000 women found that pre-pregnancy BMI and gestational weight gain are associated with pregnancy complications, and obese mothers with high weight gain during pregnancy are at the highest risk of these complications. Being overweight or obese increases your risk of:

• Cesarean delivery. Overweight women are roughly 50 percent more likely to have a c-section than women who are at a normal weight, and obese women are twice as likely to have a cesarean.
• Preterm birth. One Swedish study of over a million pregnancies found that maternal overweight and obesity during pregnancy were associated with increased risks of preterm delivery (both spontaneous and medically induced), especially extremely preterm delivery.
• Pregnancy loss and stillbirth. The higher the woman's BMI, the greater the risk of stillbirth.

Are there any risks for your baby?

Here are some conditions and situations that might affect your baby if you're plus sized and pregnant:

Large baby

While most plus-size women have average-size babies (around 7 pounds), obesity is considered a risk factor for macrosomia, or having a large baby (at least 9 pounds, 15 ounces). About 1 percent of babies are macrosomic. Your baby is more likely to be large if you have undiagnosed or poorly managed gestational diabetes, have a family history of large babies, or go past your due date.

If your fundal measurements – the distance from your pubic bone to the top of your uterus – indicate you're measuring large for dates, that may mean you're carrying a large baby. But it could also be due to a large amount of amniotic fluid or extra abdominal tissue on your belly. (Fundal measurements are more likely to be inaccurate in plus-size women.)

An ultrasound is a more accurate estimate of fetal size. However, the only real proof of a macrosomic baby is the post-birth weigh-in. Ultrasounds at term are estimates with an expected accuracy of plus or minus 10 percent.

Having a large baby can increase the risk of cesarean birth. And babies born with too much body fat are at greater risk of developing obesity later in life.

Birth defects

Researchers aren't sure why, but if you're overweight or obese, your baby has an increased risk of birth defects, such as heart defects and neural tube defects (NTDs).

Neural tube defects (NTDs) are problems with how a baby's brain and spinal cord develop. The overall risk is very small (around 1 in 1,000 births), but overweight and obese women are twice as likely to have a baby with an NTD as women at a normal weight.

You can also ask your healthcare provider for a screening test between 15 to 20 weeks to screen for NTDs, using the hormone alpha fetal protein or AFP. If that test suggests a possible problem, ultrasound and amniocentesis can provide more information.

How to stay healthy and lower the risk of complications if you’re plus size

It's true that the best way to decrease the risk of complications caused by obesity is to lose weight before you become pregnant. Even a small reduction in weight can result in improved outcomes. But if you're already pregnant and obese, don't worry – you can still have a healthy pregnancy and baby. Being diligent about these things will help:

• Seek good prenatal care. Work closely with your doctor or midwife throughout your pregnancy. Pregnant women who are overweight sometimes delay or avoid seeing a prenatal provider because they're afraid of being judged. It's very important to get regular prenatal care to monitor for complications, manage your weight, and learn about and prepare for any special considerations for your pregnancy, labor, and delivery.
  
  Find a doctor you're comfortable with, even if that means meeting multiple providers. Also keep in mind that some community hospitals and birth centers aren't equipped with the special equipment and staff to safely care for extremely obese women (those with a BMI over 50). You may need to travel to a larger hospital or academic center to get the care you need.
  
  You'll be working hand-in-hand, so it's important to have a healthcare provider you feel good about during your pregnancy. You might find our article on how to choose an ob-gyn helpful. And if you're deciding between a midwife or a doctor for your prenatal care, you'll want to read our article Midwife vs doctor: Which is right for you?

• Gain the right amount of weight for your pregnancy. The Centers for Disease Control and Prevention (CDC) recommends that overweight women gain a total of 15 to 25 pounds and obese women gain 11 to 20 pounds. (If you're pregnant with twins, those numbers are 31 to 50 pounds for overweight women and 25 to 42 pounds for obese women.). Only about one-third of women gain the recommended amount of weight during pregnancy.
• Eat healthfully. This isn't the time for a weight loss diet, but make every calorie count. Skip foods with no nutritional value in favor of those that provide nutrients for you and your baby. Aim for a nutrient-dense diet that focuses on lean protein, healthy fats, and produce – with limited added sugars. If you're managing specific conditions – such as gestational diabetes – learn all you can about the condition and follow your caregiver's advice about the role of nutrition in managing it.
• Take your daily prenatal vitamin. In addition to basic vitamins and minerals, your prenatal vitamin also contains the folic acid, calcium, and iodine your body needs during pregnancy. Ask your doctor or midwife if you need additional supplementation of any of these (or other) nutrients.
• Stay hydrated. The American College of Obstetricians and Gynecologists and the Institute of Medicine recommend that pregnant women drink 10 8-ounce glasses of water each day to stay hydrated. If you're plus sized, you need even more water than smaller women. The best way to tell if you're getting enough water is to look at your urine. If you're drinking enough, it should be pale yellow or colorless, not dark.
• Stay active. Work with your doctor or midwife to come up with a good exercise program. The CDC recommends you get at least 150 minutes weekly of moderate-intensity aerobic exercise during pregnancy. Prenatal exercise can help lower your risk of complications such as gestational diabetes and preeclampsia, manage your weight gain, and prepare you for labor and delivery. The most important thing to remember is to keep moving – even if you're just taking walks after meals. Stay active!
• Learn about any conditions that may affect you. If you're at risk for gestational diabetes or hypertension, for example, learn all you can about how you can manage or prevent the condition. Follow your healthcare provider's advice, and call your provider right away if you experience signs of problems, such as a severe or persistent headache, rapid weight gain, intense pain or tenderness in your upper abdomen, puffiness or swelling in your face or extremities, or vision changes. It's also a good idea to become familiar with pregnancy symptoms you should never ignore.