Being pregnant with twins, triplets and other multiples

What causes you to get pregnant with multiples?

A multiple pregnancy means you’re pregnant with more than one baby. 

Multiple pregnancy usually happens when more than one egg is fertilized. It also can happen when one egg is fertilized and then splits into 2 or more embryos that grow into 2 or more babies. 

When one fertilized egg splits into 2, the babies are called identical twins. They look almost exactly alike and share the exact same genes. When two separate eggs are fertilized by two separate sperm, the babies are called fraternal twins. They don’t share the same genes and are no more alike than any siblings from different pregnancies with the same parents.

Singletons, or one baby, are the most common type of pregnancy. However, more people are getting pregnant with multiples now than in the past. This is mostly because more people are having babies later in life, and multiples are more common among parents who are older than 30. Also, more people are using fertility treatments to get pregnant. Multiples are also more common among people who use fertility treatment.

How do you know if you’re pregnant with multiples? 

You may be pregnant with multiples if: 

• Your breasts are very sore.
• You’re very hungry or you gain weight quickly in the first trimester.
• You feel movement in different parts of your belly at the same time. 
• You have severe morning sickness. Morning sickness is nausea (feeling sick to your stomach) and vomiting that happens in the first few months of pregnancy. 
• Your health care provider hears more than one heartbeat or finds that your uterus is larger than usual. 
• You have high levels of a hormone called human chorionic gonadotrophin (also called hCG) or a protein called alpha-fetoprotein in your blood. HCG is a hormone your body makes during pregnancy. Alpha-fetoprotein is a protein that a developing baby makes during pregnancy. 

Your provider can use ultrasound to find out for sure if you’re pregnant with multiples. Ultrasound uses sound waves and a computer screen to show a picture of a baby.

What kind of prenatal care do you need if you’re pregnant with multiples?

If you’re pregnant with multiples, you may need extra medical care during pregnancy, labor and birth. You may need to go to extra prenatal care checkups so your provider can watch you and your babies for problems. You also may need more prenatal tests (such as ultrasounds) to check on your growing babies throughout your pregnancy. 

If you’ve had pregnancy complications in the past or if you have health conditions that put you at risk for pregnancy complications, your provider may refer you to a maternal-fetal medicine specialist. This is a doctor who specializes in high-risk pregnancies. High-risk means you’re more likely than most pregnant people to have problems with your pregnancy. If you’re referred to this kind of doctor, it doesn’t mean you’ll have problems during pregnancy. It just means they can check you and your babies more closely to help prevent or treat any conditions that may happen.  

How can a multiple pregnancy affect your health?

The following complications are more common in people who are pregnant with multiples:

• Preterm labor. This is labor that happens too early, before 37 weeks of pregnancy. Preterm labor can lead to premature birth (birth before 37 weeks of pregnancy).
• Anemia. Anemia is when you don’t have enough healthy red blood cells to carry oxygen to the rest of your body. A condition called iron-deficiency anemia is common in multiple pregnancies and can increase your chances of premature birth. Your provider may prescribe an iron supplement for you to make sure you’re getting enough iron. 
• Gestational diabetes. This is a kind of diabetes that only pregnant people can get. If untreated, it can cause serious health problems for you and your babies. Diabetes is when you have too much sugar (called blood sugar or glucose) in your blood.
• Gestational hypertension or preeclampsia. These are types of high blood pressure that only pregnant people can get. High blood pressure is when the force of blood against the walls of your blood vessels is too high. It can cause problems during pregnancy. Preeclampsia is a condition that can happen after the 20th week of pregnancy or right after pregnancy. It’s when a pregnant person has high blood pressure and signs that some of their organs, like the kidneys and liver, may not be working properly.
• Hyperemesis gravidarum. This is severe nausea and vomiting.
• Intrahepatic cholestasis of pregnancy (also called ICP). ICP is a liver condition that slows the normal flow of bile, causing bile to build up in the liver. Bile is a fluid that helps your body break down fats and helps the liver get rid of toxins (poisonous substances). This buildup can cause chemicals called bile acids to spill into your blood and tissues, leading to severe itching.
• Polyhydramnios. This is when there’s too much amniotic fluid. Amniotic fluid is the fluid that surrounds the baby in the uterus. 
• Miscarriage or stillbirth. Miscarriage is when a baby dies before 20 weeks of pregnancy. Stillbirth is when a baby dies after 20 weeks of pregnancy. Some people who are pregnant with multiples have a condition called vanishing twin syndrome. This is when one or more babies die during the pregnancy and one baby survives. 
• Postpartum depression (also called PPD). This is a kind of depression that some parents get after having a baby. PPD is strong feelings of sadness that last for a long time. These feelings can make it hard for you to take care of your baby. 
• Postpartum hemorrhage. This is heavy bleeding after giving birth. It’s a serious but rare condition. 

How can being pregnant with multiples affect your babies’ health?

If you’re pregnant with multiples, your babies are more likely to have health complications, including: 

• Preterm birth. Premature babies (born before 37 weeks of pregnancy) may have more health problems or need to stay in the hospital longer than babies who are born close to their due date. Some may spend time in a hospital’s newborn intensive care unit (also called NICU). Premature babies also may have  health problems that can affect them later in life. More than half of twins and nearly all triplets and other higher-order multiples are born earlier than they should be.
• Birth defects. Birth defects are health conditions that are present at birth. They change the shape or function of one or more parts of the body. Birth defects can cause problems in overall health, how the body develops or how the body works. Multiples are about twice as likely as singleton babies to have birth defects, including neural tube defects (such as spina bifida), cerebral palsy, congenital heart defects and birth defects that affect the digestive system.
• Growth problems. Multiples are usually smaller than singleton babies. Your provider can use ultrasound to check your babies’ growth at prenatal care checkups. When one twin is much smaller than the other, they’re called discordant twins. Discordant twins are more likely to have health problems during pregnancy and after birth. 
• Low birthweight. This is when your baby is born weighing less than 5 pounds, 8 ounces. Babies whose weight is lower than it should be at birth are more likely than babies born at a normal weight to have certain health problems, such as retinopathy of prematurity. They’re also more likely to have health problems later in life, like high blood pressure. More than half of twins and nearly all higher order multiples weigh less than they should at birth.
• Twin-twin transfusion syndrome. This condition happens when identical twins share a placenta and one baby gets too much blood flow, while the other baby doesn’t get enough. The placenta grows in the uterus and supplies your babies with food and oxygen through the umbilical cord. Twin-twin transfusion syndrome can be treated with laser surgery to seal off the connection between the babies’ blood vessels and amniocentesis to drain off extra fluid. 
• Neonatal death. This is when a baby dies in the first 28 days of life. Preterm birth is the most common cause of neonatal death.

What makes you more likely to get pregnant with multiples?

You may be more likely to get pregnant with more than one baby if:

• You have fertility treatment. If you’re having fertility treatment, it’s important to try to get pregnant with just one baby. For example, if you’re having a treatment called in vitro fertilization (also called IVF), you can have just one embryo placed in your uterus. This is called single embryo transfer. In IVF, an egg and sperm are combined in a lab to create an embryo (fertilized egg) which is then placed in the uterus. If you’re having any kind of fertility treatment, talk with your provider about ways to lower the chance of getting pregnant with multiples. 
• You’re in your 30s, especially your late 30s. If you’re 30 or older, you’re more likely than younger people to release more than one egg during a menstrual cycle.
• You have relatives who have had multiples.  If you or other people in your family have had fraternal twins, you may be more likely to have twins, too. You’re also more likely to have multiples if you’ve been pregnant before, especially if you’ve been pregnant with multiples.   
• You’re a person who has obesity. If your body mass index (also called BMI) is 30 or higher. To find out your BMI, go to cdc.gov/bmi.
• You’re Black or White. Black people are more likely to have twins than other parents. White people, especially those older than 35 years old, are most likely to have higher-order multiples. 

How are multiples born?

Vaginal birth is the way most babies are born. During vaginal birth, the uterus contracts to help push the baby out.

If you’re pregnant with multiples, you’re more likely to have a cesarean birth (also called c-section) than if you’re pregnant with one baby. During a c-section, the doctor makes a cut in the belly and uterus to remove the baby. Most triplets and higher-order multiples are born by c-section.

If you’re pregnant with twins, you may need a c-section if neither baby is in the head-down position or if you have other complications. You may be able to have a vaginal birth if:

• Both babies are in the head-down position and you have no other complications
• The lower twin is in the head-down position but the higher twin isn’t. 

Do you need to eat special foods if you’re pregnant with multiples? 

No. But you do need more of certain nutrients, such as folic acid, protein, iron and calcium. You can get the right amount of these nutrients by eating healthy foods and taking your prenatal vitamin every day. Prenatal vitamins are multivitamins made just for pregnant people. Compared to a regular multivitamin, they have more of some nutrients that you need during pregnancy. Your provider can prescribe a prenatal vitamin for you at your first prenatal care checkup. Even when you’re pregnant with multiples, you only need to take one prenatal vitamin each day. 

How much weight should you gain if you’re pregnant with multiples?

If you’re pregnant with multiples, you need to gain more weight than if you were pregnant with one baby. The amount of weight to gain depends on your weight before pregnancy and how many babies you have. Talk with your provider about how much weight to gain.  

Here’s what you should know about gaining weight if you’re pregnant with twins: 

• If you were at a healthy weight before pregnancy, you want to gain about 37 to 54 pounds during pregnancy. 
• If you were overweight before pregnancy, you want to gain about 31 to 50 pounds during pregnancy. 
• If you were affected by obesity before pregnancy, you want to gain about 25 to 42 pounds during pregnancy. 

Do you need to limit physical activity if you’re pregnant with multiples?

Talk with your provider about what kind of activities are safe for you to do. You may need to cut out any high-impact activities, such as aerobics or jogging, that make you jump or put stress on your joints. You may be able to do some activities, such as swimming, prenatal yoga or walking. 

Later in pregnancy, you may need to limit physical activity, including travel and work. Many people who are pregnant with multiples go on bed rest. Bed rest means reducing your activities while you’re pregnant. Bed rest may mean staying in bed all day or just resting a few times each day.  

More information

• Centers for Disease Control and Prevention (CDC)
• Show Your Love Preconception Health

Updated June, 2021