Twin Pregnancy Complications

A twin pregnancy carries specific risks and complications for both the baby and mother. The maternal-fetal medicine experts at Brigham and Women’s Hospital provide expert, multi-disciplinary care and are committed to doing everything possible to ensure the health of mothers and their babies.

Common Fetal Complications

What is preterm delivery?

The most common complication for a twin pregnancy is preterm delivery, a delivery that occurs before 37 weeks.

About half of all twin pregnancies are delivered around 36 weeks. This can cause low birth weight, as well as feeding and breathing difficulties for the twins. Unfortunately, there are limited treatment methods to prevent preterm delivery.

The clinical management of preterm delivery in twin gestation is complex. If your obstetric care provider is concerned that you may deliver your twins prematurely, several therapies can be discussed:

  • Maternal steroid administration includes two intramuscular injections of betamethasone 24 hours apart to accelerate the babies’ lung development (administered from 24 weeks to 34 weeks) and provide benefits to the babies’ other developing systems.
  • Magnesium sulfate infusion through an IV line to the mother reduces the severity and risk of cerebral palsy associated with preterm newborn babies (administered from 24 to 32 weeks).
  • Routine hospitalization and bed rest have not been shown to decrease the risk of preterm labor in twin pregnancies.
  • Medications that stop contractions (tocolytics) are helpful when receiving the course of steroid injections over 48 hours, but they are not recommended for long-term use during pregnancy.
  • The use of vaginal progesterone for shortened cervix in twin pregnancies is controversial, but it seems a reasonable option in certain clinical situations.
  • The insertion of an Arabin pessary might be helpful in twin pregnancies with a short cervix and at risk of preterm delivery. (See below for more information about this method.)

What is an arabin pessary?

This device is a soft, flexible ring that is placed inside of the mother’s vagina by her obstetric care provider to help prevent preterm labor in those patients who are at higher risk, including those with a shorter cervix.

Arabin Pessary diagram

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Very few studies have used the Arabin pessary in women with twin pregnancies and a short cervix to prevent preterm delivery. The results are difficult to generalize and validate; however, we recommend using this method for mothers who meet the right clinical requirements because it is non-invasive and not thought to cause harm to the fetus or mother.

Once the Arabin pessary is inserted, it does not need to be removed until delivery. It can cause a white, watery vaginal discharge that it is sometimes confused with rupture of membranes. The vaginal discharge is normal and there is no reason for concern.

What is intrauterine growth restriction (IUGR)?

Intrauterine growth restriction (IUGR) is a condition where an unborn baby grows more slowly than the normal rate. Twins are at a higher risk of IUGR, which can lead to a preterm delivery.

Your obstetric care provider can determine if your twins are affected with IUGR by serial growth ultrasounds.

If your obstetric care determines that one, or both twins, is not growing at the proper rate or falls below the 10th percentile on the growth curve for gestational age, you will need to increase the frequency of office visits and the surveillance of your babies with ultrasounds and fetal testing.

What is twin-to-twin transfusion syndrome (TTTS)?

Mo-Di twins share a placenta, so it is likely that they share vascular connections. Unequal blood sharing in the vessels, occurring in about 15% of Mo-Di pregnancies, is called twin-to-twin transfusion syndrome (TTTS) and can be potentially dangerous.

Diagnosing TTTS

  • TTTS is diagnosed using ultrasound surveillance to measure the twins’ amniotic fluid.
  • If one twin’s maximum vertical pocket is less than two centimeters and the other’s is greater than eight centimeters, TTTS is confirmed.

Potential Dangers of TTTS

  • TTTS causes one twin to become larger than the other. The larger twin is called the recipient and the smaller twin is called the donor.
  • The recipient’s increased blood flow makes this twin produce more urine than usual. This may cause an excessive accumulation of amniotic fluid (polyhydramnios) or a form of heart failure for the babies called hydrops.
  • The donor twin produces less urine than usual. This may cause a low level of amniotic fluid (oligohydramnios) and a small bladder.
  • TTTS is classified in 5 progressive stages and the progression of TTTS can be unpredictable. However, most cases stay in Stage I with fluctuating levels of amniotic fluid.
  • Survival rates vary from 15-70%, depending on the twins’ age at diagnosis and the severity.

Managing TTTS

  • A minimally invasive surgical procedure—called fetoscopic laser photocoagulation—is considered the best available approach for twins with TTTS stages II, III, and IV of TTTS before 26 weeks. This procedure disconnects the vascular connections between the twins. It is offered only at specialized treatment centers.
  • Amnioreduction removes excess amniotic fluid from the recipient twin. This procedure may help alleviate the mother’s discomfort caused from the extra fluid.
  • Careful supervision (often referred to as “expectant management”) is needed throughout the pregnancy, even if a procedure is not required.

Delivering Twins with TTTS

  • The best time to deliver twins with TTTS depends on a number of factors, including disease stage and severity, progression, the effect of interventions and results of antenatal testing.
  • We recommend delivering at 34-36 weeks for most twins with TTTS.

What is unequal placental sharing?

This condition is sometimes difficult to distinguish from TTTS. When monochorionic twins differ in size by more than 20% this is most likely due to unequal sharing of the placenta. Those pregnancies with at least one growth-restricted fetus and twin growth discordance of more than 20% are at higher risk of neonatal morbidity. Pregnancies affected by twin growth discordance should have closer surveillance.

What is twin reversal arterial perfusion syndrome (TRAP)?

Twin reversal arterial perfusion syndrome (TRAP) is a rare condition that affects monochorionic twins (Mo-Di and Mo-Mo). With TRAP, one twin does not develop a normal heart and brain structures but receives blood supply from the other, normally developing twin. Because the normal twin must pump an excess amount of blood, this strains the twin’s heart and increases the risk of heart failure. If untreated, TRAP is a very serious condition.

Stopping the extra blood pumped between twins is the only way to treat this condition.

This is done with a small intrauterine minimally invasive surgery. Radiofrequency ablation is used inside the uterus to end the blood flow from the umbilical cord to the underdeveloped twin. With this technique, there’s a high chance that the normally developing twin will survive.

What is cord entanglement with MO-MO twins?

Mo-Mo twins share an amniotic sac, so it is common for their umbilical cords to become entangled during the pregnancy.

Entanglement increases the risk that the cords will compress and interrupt blood flow to one or both twins. This can cause unexpected and potentially life-threatening distress for one or both twins.

If carrying Mo-Mo twins, we recommend:

  • Admission to the hospital at 24-28 weeks for daily surveillance by maternal-fetal medicine specialists.
  • Delivery via Cesarean section at 32-34 weeks.

Common Maternal Complications

What should I expect if I have gestational diabetes?

While carrying twins, you will have a larger placental size than a singleton pregnancy. A larger placenta produces more pregnancy hormones, which makes the occurrence of gestational diabetes more likely. It is very common and is usually temporary, resolving after pregnancy.

All pregnant women are screened for gestational diabetes in the third trimester, typically between 24-28 weeks. The screening test involves drinking a very sweet drink and then drawing your blood one hour later. You do not need to be fasting for the test.

If the screening test is positive, you will take a diagnostic test. This test is very similar to the initial test but you need to be fasting and your blood will be drawn 1, 2 and 3 hours after drinking the sweet drink.

If you are diagnosed with gestational diabetes, you will need to:

  • Monitor your glucose levels at least four times per day.
  • Consult with a nutritionist to manage your diet and exercise. If necessary, you might require medical therapy to control your blood sugars.
  • You will have to increase the frequency of office visits and surveillance of your babies with ultrasounds and fetal testing.
  • In some cases, you might need a consult with a maternal-fetal medicine specialist.

What should I expect if I have a hypertensive disorder?

When carrying twins, you may be more likely to develop high blood pressure. This is defined as a systolic blood pressure equal or higher than 140 and a diastolic blood pressure equal or higher than 90. If combined with the spilling of protein in the urine, laboratory abnormalities or symptoms (for example, headache, visual changes and right upper-quadrant pain), this condition is called preeclampsia and it can be more serious.

If you are diagnosed with hypertension or preeclampsia, you will need to:

  • Increase the frequency of office visits and the surveillance of your babies with ultrasounds and fetal testing.
  • In some cases, you might need a consult with a maternal-fetal medicine specialist.
  • You may require antihypertensive medication, hospitalization and or early delivery.

What should I expect if I have heartburn during pregnancy?

Gastroesophageal reflux disease, also known as GERD and heartburn, frequently affects mothers carrying twins.

Small changes in lifestyle and diet can lessen the severity effectively, including:

  • Eating your last meal of the day at least 3 hours before bedtime
  • Elevating your head during sleep
  • Avoiding dietary triggers
  • Taking an antacid approved by your obstetric care provider (most antacids are considered safe during pregnancy and breastfeeding)

What can I do to help sciatica and low-back pain in twin pregnancies?

Pain or tingling in the leg—a condition called sciatica—and low-back pain are more common during a twin pregnancy but are not considered dangerous. If you experience this discomfort, consider:

  • Wearing shoes with good arch support
  • lifting objects carefully by squatting down, lifting your knees, and keeping your back straight
  • Asking for help lifting heavy objects
  • Placing a board between the mattress and box spring if your bed is too soft
  • Sitting in chairs with good back support or using a small pillow to provide additional support
  • Sleeping on your side with pillows between your knees for additional support
  • Massaging or applying heat or cold to the painful area
  • Pain relievers may be used to help alleviate severe pain

How do I ask additional questions?

We are happy to respond to general questions about twin pregnancies. Please use our online form to send us your twin pregnancy question, and one of our maternal-fetal medicine specialists will respond. Please note that your question will be emailed and responded through a private and secure system.

Do you have additional resources on twin pregnancy?

Learn about obstetric services provided by Brigham and Women’s Hospital.

Read more about maternal-fetal medicine at Brigham and Women’s Hospital.

Common questions and answers for women expecting twins from the American College of Obstetrics and Gynecology.

Social support organizations offer helpful information.


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