Patient education: Having twins (The Basics)

What are identical twins, and how do they happen? — Identical twins happen when 1 egg is fertilized by 1 sperm and then splits (soon after it is fertilized) to form 2 embryos. An "embryo" is the term doctors use to describe when a baby starts to grow. Each embryo grows into a baby.

Identical twins have all of the same genes. They are the same sex and look very much alike. Identical twins are less common than fraternal twins.

What are fraternal twins, and how do they happen? — Fraternal twins happen when 2 different eggs are fertilized by 2 different sperm. Then, there are 2 embryos, each of which grows into a baby.

Fraternal twins share some, but not all, of the same genes. They are like any 2 siblings, but just share the same birthday. Fraternal twins can be 2 girls, 2 boys, or a boy and a girl.

What increases the chances of having twins? — Certain things increase your chances of having twins. These include:

●Being in your 30s or older

●Taking medicine to help get pregnant

●Having a procedure called "in vitro fertilization" ("IVF") to help get pregnant

●Your race – Twin pregnancies are more common in Black people than in Asian or White people.

●Having a family history of twins

These things mostly increase the chances of having fraternal twins only, not identical twins.

How does my doctor or midwife know that I'm having twins? — When your doctor or midwife examines you, they will feel the size of your uterus (figure 1). People who are having twins usually have a uterus that is bigger than expected, given their due date. Also, early in pregnancy, your doctor or midwife will probably do a test called an ultrasound. An ultrasound uses sound waves to create pictures of the inside of your body. This shows how many embryos or babies are in your uterus.

Will I need special prenatal care? — Yes. If you are pregnant with twins, you will need special prenatal care. You will see your doctor or midwife more often. You will also have frequent ultrasounds to check how your babies are growing. Later in your pregnancy, you might have other tests to check your babies' health.

What should I know about having twins? — Having twins is a bit different than having only 1 baby. Your doctor or midwife will talk with you about how much weight you should gain and how active you should be.

They will also talk with you about problems that are more likely to happen when a person is pregnant with twins. The most common problem is that the babies will be born too early, before 37 weeks of pregnancy (3 or more weeks before the due date). Doctors use the word "premature" or "preterm" for babies who are born too early.

Being born too early is sometimes a problem. Preterm babies are more likely to be smaller and need to stay in the hospital for longer after birth. They are also more likely to have medical problems, such as breathing problems.

If your twins are identical, your doctor or midwife will use ultrasounds to check for a problem called "twin-to-twin transfusion syndrome." This is a problem with the placenta that can sometimes happen in a pregnancy with identical twins. (The placenta is the organ inside the uterus that brings a baby nutrients and oxygen, and carries away waste.) If you have this problem, your doctor or midwife will monitor you closely and suggest treatment if needed.

People who are carrying twins are also more likely to get high blood pressure during pregnancy.

How will I deliver my babies? — It depends on the position of the babies in your uterus, your health, and your babies' health. If you and your babies are healthy and the first baby is coming head-first, you might be able to deliver your babies vaginally. If not, the doctor will probably do a c-section (surgery to get the babies out).

How do I know if my twins are identical or fraternal? — Twins of the opposite sex are always fraternal. Twins of the same sex can be fraternal or identical.

If your twins are the same sex, your doctor or midwife might be able to tell if they are identical by checking your placenta. They can use ultrasound to do this before birth, or examine the placenta after birth. Sometimes, the only way to tell if twins are identical is by doing blood tests on the babies after they are born.

Can I breastfeed my babies? — If you would like to. Most people make enough milk to breastfeed twins. If your babies are born too early, you might need to pump and store your breast milk until your babies are able to drink it.

You will probably want to work with a breastfeeding expert, called a "lactation consultant." That way, you can find a schedule and way of breastfeeding that works best for you and your babies.

What if I am having a tough time taking care of my babies? — If you are having a tough time, try to get some help. Taking care of twins can be tiring and stressful. You might want to ask friends or relatives to help you. Many parents also find it helpful to join a support group for parents of twins. That way, they can talk to others in the same situation.

More on this topic

Patient education: When a baby is born premature (The Basics)
Patient education: When your baby is measuring small during pregnancy (The Basics)
Patient education: What to expect in the NICU (The Basics)
Patient education: Preterm labor (The Basics)
Patient education: Cesarean birth (The Basics)
Patient education: Prenatal care (The Basics)
Patient education: Deciding to breastfeed (The Basics)
Patient education: Breastfeeding (The Basics)
Patient education: Pumping and storing breast milk (The Basics)
Patient education: Preeclampsia (The Basics)

Patient education: Preterm labor (Beyond the Basics)
Patient education: C-section (cesarean delivery) (Beyond the Basics)
Patient education: Breastfeeding guide (Beyond the Basics)
Patient education: Preeclampsia (Beyond the Basics)