What You Need to Know About a Twin Pregnancy

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Pregnancy is often an exciting and gratifying experience, but when you are expecting twins, there is more to consider. Read on to learn what to expect and possible complications you may experience if you’re pregnant with twins.

newborn fraternal twins in hospital sleep together

Jill Lehmann Photography / Getty Images


Conception happens when the sperm fertilizes an egg within days of ovulation.

Menstrual cycles average 28 days and ovulation typically happens mid-cycle—around day 14. A woman’s ovary normally releases one egg during ovulation. There are two ways twin pregnancies can occur:

  • Fraternal twins: When one or both ovaries release more than one egg during ovulation and each egg is fertilized and implants in the uterus.
  • Identical twins: When a single fertilized egg splits into two identical embryos.

Identical twins are rarer than fraternal twins.

What Increases Your Chance of Conceiving Twins?

Twin pregnancies are more common in people who:

  • Are older than 35 years old
  • Have a family history of twins
  • Have a partner with a twin
  • Have conceived through in vitro fertilization (IVF)

The first definitive symptom of any pregnancy is missing a period. While it may take awhile before you know you are carrying twins, there are some indicators.


Women pregnant with twins have the normal symptoms of a single pregnancy, but oftentimes they are more pronounced.

For example, if you’re pregnant with twins, your human chorionic gonadotropin (hCG) levels will rise faster and higher than in a single pregnancy. More of this hormone makes nausea more severe. Fatigue and breast tenderness are other symptoms in the first trimester that may be worse than if you were pregnant with a single fetus.

Additionally, you will gain more weight, which puts more strain on your body as your pregnancy progresses, and can cause more exaggerated symptoms such as swelling and body aches.

Weight Gain for Twin Pregnancies

Gestational weight gain for twin pregnancies is as follows:

  • 37 to 54 pounds for normal-weight women
  • 31 to 50 pounds for overweight women
  • 25 to 42 pounds for obese women

It is important to keep your weight as close to these guidelines as possible through healthy eating and exercise to lessen the additional risks associated with having twins.

First Healthcare Provider’s Visit

Prenatal care is critical during pregnancy. If you conceive naturally, your first OB visit usually happens toward the end of your first trimester. If you conceive through IVF, you may see your healthcare provider sooner. Either way, the first major checkup usually happens toward the end of the first trimester (about nine to 12 weeks), even if you have seen your healthcare provider sooner than this. This visit may be when you learn that you are having twins.

During this appointment, your healthcare provider will review your health history, perform physical and pelvic exams, and give an overview for treatment during your pregnancy. Preparing a list of questions to ask your healthcare provider will help you remember them.

Most women will also get the first ultrasound of their fetuses to check their heartbeats and anatomy. Your healthcare provider will run other tests to check for genetic abnormalities in the babies through bloodwork. Sometimes you may be offered a blood test that will reveal the gender of the fetuses. Your healthcare provider will calculate how many weeks pregnant you are and set a due date for the babies.

After the first visit, the standard schedule to see your OB-GYN is:

  • Every four weeks until 28 weeks
  • Every two to three weeks from 28 to 36 weeks
  • Weekly from 36 weeks until delivery

You may need to see your OB-GYN more frequently than the standard schedule.

Seeing a Perinatologist

Because having twins is considered a high-risk pregnancy, you will likely be referred to a perinatologist (high-risk obstetrics specialist or maternal fetal medicine specialist) to partner with your OB-GYN in your care.

Risks and Complications

Carrying two babies is more taxing on your body than a single pregnancy. A number of risks are associated with twin pregnancies, and a number of complications may occur. The following are the most prevalent.

Preterm Labor and Birth

Preterm labor and birth are the most common complications in twin pregnancies. Preterm is defined as delivering a baby before 37 weeks gestation. Twin pregnancies average 36 weeks long.

Both being pregnant with twins and using assisted reproductive technology are associated with a higher risk of preterm labor and birth. One study showed that more than 50% of twin births occurred preterm, compared with only 10% of births of single babies.

Complications of preterm delivery depend on how early the babies are delivered. The earlier they are born, the higher the risk for complications. These can include:

Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) or small for gestational age (SGA) is a condition that happens when one or more of your babies isn’t growing at the proper pace. This condition might cause the babies to be delivered prematurely or at a low birth weight. Nearly half of pregnancies with more than one baby have this problem.

Your healthcare provider will monitor your pregnancy for IUGR, usually by ultrasound, to ensure your babies’ development is on track. Babies born with IUGR are at an increased risk for:

  • Birth by C-section
  • Hypoxia (lack of oxygen when a baby is born)
  • Meconium aspiration, which is when a baby swallows part of the first bowel movement
  • Hypoglycemia (low blood sugar)
  • Polycythemia (increased number of red blood cells)
  • Hyperviscosity (decreased blood flow due to an increased number of red blood cells)
  • Motor and neurological disabilities

Your healthcare provider may manage IUGR with:

  • Frequent monitoring with ultrasounds
  • Tracking fetal movements
  • Corticosteroid drugs
  • Hospitalization
  • Early delivery and sometimes an emergency C-section

When to deliver for a woman with IUGR will often depend on:

  • Gestational age
  • Fetal well-being
  • The amount of amniotic fluid


Preeclampsia is when a woman develops high blood pressure and a protein in her urine during pregnancy. There is a greater chance of preeclampsia with twin pregnancies. It also may occur earlier and be more severe in pregnancies with multiples.

Does Preeclampsia Go Away After Delivery?

Preeclampsia usually starts any time after 20 weeks of pregnancy or after childbirth. This condition usually resolves shortly after birth.

Preeclampsia can damage many organs in your body, most commonly:

  • Kidneys
  • Liver
  • Brain
  • Eyes

Preeclampsia can also:

  • Put a baby’s health at risk
  • Cause placental abruption
  • Cause low birth weight
  • Cause preterm birth

Because of the risks involved for mom and babies, when preeclampsia occurs during pregnancy, the babies may need to be delivered early even if they are not not full term.

Signs of preeclampsia include:

  • Headaches
  • Blurry vision
  • Dark spots appearing in your vision
  • Right side abdominal pain
  • Rapid swelling in the hands and face (edema)
  • Rapid weight gain

You can lower your risk of preeclampsia by maintaining a healthy weight, exercising, and following a healthy diet before pregnancy. All of these steps are even more important during pregnancy per your healthcare provider’s orders.

The U.S. Preventive Services Task Force recommends the use of daily low-dose aspirin (81 milligrams) after 12 weeks of pregnancy to help prevent preeclampsia in those at high risk.

Still, some women develop preeclampsia despite taking preventive measures. Women with preeclampsia, especially those carrying twins, require close monitoring by their healthcare provider because of potentially serious complications.

Low Birth Weight

Low birth weight is another common complication with twin pregnancies since many twin pregnancies are preterm deliveries. Low birth weight is defined as a baby weighing less than 5 pounds 8 ounces at birth.

  • Babies weighing less than 1,500 grams (3 pounds, 5 ounces) at birth are considered very low birth weight.
  • Babies weighing less than 1,000 grams (2 pounds, 3 ounces) at birth are considered extremely low birth weight.

The two main causes of low birth weight are:

  • Prematurity: Babies born prematurely (before 37 weeks) primarily account for low birth weight babies. Significant weight gain occurs in the last weeks of pregnancy, so by delivering early, a baby misses the final growth stages.
  • Intrauterine growth restriction: Discussed above, this is another condition that accounts for low birth weight, but in a full-term baby.

Complications for low birth weight babies include:

  • Low oxygen levels at birth
  • Trouble staying warm
  • Trouble feeding and gaining weight
  • Infection
  • Breathing problems and immature lungs (infant respiratory distress syndrome)
  • Nervous system problems, such as bleeding inside the brain
  • Digestive problems
  • Sudden infant death syndrome (SIDS)

Nearly all low birth weight babies require time in the neonatal intensive care unit (NICU) until they weigh enough and are well enough to go home.

Gestational Diabetes

Gestational diabetes—which is high blood glucose (sugar) levels during pregnancy—impacts twin pregnancies more often than single pregnancies.

Pregnant women are routinely tested between 24 and 28 weeks for gestational diabetes because of the risks this condition poses. You may be screened earlier if you are at a higher risk for gestational diabetes. Risk factors include:

  • Being overweight or obese
  • Having gestational diabetes in a previous pregnancy
  • Having high blood pressure
  • Having a history of heart disease
  • Having polycystic ovary syndrome (PCOS)

Uncontrolled blood sugar can cause complications during pregnancy for mothers and babies including:

  • Large babies: Uncontrolled blood sugar in a mother drives up babies’ blood sugar, too. This can lead to babies growing too big.
  • C-section: Women whose blood sugar isn’t well controlled have a higher risk of delivery by cesarean.
  • Preeclampsia: Preeclampsia is already more common in twin pregnancies. Women with diabetes have high blood pressure more often than women without diabetes.
  • Hypoglycemia (low blood sugar): This is a potentially life-threatening side effect from taking medications to control blood sugar.

In many cases, gestational diabetes can be managed through exercise and a healthy diet. However, some women will also require treatment with insulin.

Placental Abruption

The placenta attaches the fetuses to the mother’s uterus. It is a life source that gives food and oxygen to the fetuses through the umbilical cord. Placental abruption happens when the placenta separates from the uterus before birth. In most cases, the placenta stays attached to the uterus.

When placental abruption occurs, the uterus and all it provides is compromised. Placental abruption is an emergency and requires immediate care because it is life-threatening to the babies and potentially the mother. It can lead to:

  • Premature birth and low birth weight
  • Hemorrhaging in the mother
  • Death to a baby (in rare cases)

About 1 out of 100 pregnancies has placental abruption. This condition usually happens in the third trimester, but it can also happen after 20 weeks of pregnancy.

The most common symptom is vaginal bleeding with pain during the third trimester of pregnancy. Sometimes the blood will be behind the placenta. In that case, there will be no bleeding. Symptoms also can include:

  • Abdominal pain
  • Uterine contractions
  • Tender uterus
  • Backache

If you have these symptoms, it’s critical that you get evaluated by a healthcare provider.

Twin-to-Twin Transfusion Syndrome

In twin-to-twin transfusion syndrome (TTTS), identical twins (or other multiples) share a placenta. Within the placenta, they share a network of blood vessels that supply nutrients and oxygen essential to survive and develop in utero.

When TTTS occurs, there is an unequal sharing of blood that passes between twins through blood vessel connections in the placenta. One twin (the donor twin) pumps blood to the other twin (the recipient twin). This causes the donor twin to receive too little blood and the recipient twin to receive too much.

This unequal distribution of blood and nutrients can lead to severe complications and even death in one or both twins. When the donor twin gives away more blood than it receives in return, the fetus runs the risk of:

  • Malnourishment
  • No amniotic fluid surrounding it
  • A small or absent bladder
  • Organ failure

The recipient twin receives too much blood and is at risk for cardiac complications, including hydrops.

A critical factor in determining the prognosis of TTTS is the level of cardiovascular dysfunction in the fetuses. For this reason, TTTS diagnosis includes a detailed examination of the fetal heart by using fetal echocardiography in both the recipient and donor twin.

TTTS is confirmed by ultrasound and other specialized tests that measure amniotic fluid, blood flow, and bladder filling in the detail.

Healthcare providers use the Quintero staging system to determine the severity of TTTS.

The Stages of TTTS

Stage I is the least severe stage. More than three-fourths of stage I cases remain stable or regress without invasive intervention. Survival is high at around 86%. Advanced TTTS (stage III and higher) has a high mortality rate at 70% to 100%, especially when TTTS presents at or before 26 weeks.

Treatment options include:

  • Amniocentesis, to drain off excess fluid. This appears to improve the blood flow in the placenta and lower the risk of preterm labor. Amniocentesis can save approximately 60% of affected babies.
  • Laser surgery can also be used to seal off the connection between the blood vessels and appears to save 60% of affected babies.
  • Delivery is also an option if your babies have developed enough to survive outside the womb.


Cesarean (C-section) deliveries entail a surgical cut across the lower abdomen to remove a baby from the uterus. They are done when a vaginal delivery is not safe for a baby or mother, or when there’s a need for an emergency delivery.

C-sections are more common in twin pregnancies than single deliveries. This is because the conditions that raise the risk of C-section (low birth weight, gestational diabetes, preeclampsia, placental abruption, and IUGR) occur more often in women pregnant with twins.

However, twins are frequently delivered vaginally depending on factors relating to the presentation and gestation of the babies. Vaginal deliveries with twins are possible when:

  • The gestation is greater than 32 weeks
  • Twin A (the baby closest to the cervix) is the largest
  • Twin A is head down
  • Twin B is head down, breech, or sideways
  • Twin B is smaller than twin A
  • There is no evidence of fetal distress

C-sections are sometimes planned and sometimes not when there are emergency situations. There are some inherent risks associated with the surgery:

  • Infection
  • Blood loss
  • A blood clot that leads to embolism
  • Injury to the bowel or bladder
  • An incision that might weaken the uterine wall
  • Abnormalities of the placenta in subsequent pregnancies
  • Risks from general anesthesia
  • Fetal injury
  • The possibility you can’t have vaginal births in future pregnancies

A Word From Verywell

Pregnancy can be one of the most rewarding periods of a woman’s life. If you are pregnant with twins, it is important to maintain a close relationship with your healthcare provider to ensure the best outcomes for you and your babies.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Cherie Berkley, MS
Cherie Berkley is an award-winning journalist and multimedia storyteller covering health features for Verywell.