A twin pregnancy can be exciting news for some expecting parents, but because twin pregnancies have higher risks than singleton pregnancies, people pregnant with twins should be monitored carefully by pregnancy care providers.
Common medical complications for twins during pregnancy
Twin pregnancies are at higher risk for several complications of pregnancy, including:
Preterm birth
About 6 in 10 twin pregnancies are delivered preterm (before 37 weeks of pregnancy). Unfortunately, treating and preventing preterm labor in twin pregnancies can be less successful than in singleton pregnancies. It can be normal for people pregnant with twin pregnancies to have frequent contractions in the third trimester of pregnancy. A pregnancy care provider can help determine when to seek care.
Fetal growth restriction and growth discordance
Twins are usually monitored with ultrasounds to ensure both are growing normally. Twins are more likely to be small for their gestational age than singleton pregnancies. Being small may require additional fetal monitoring and may affect when birth is recommended. Additionally, sometimes one twin is much bigger than the other; when the larger twin is expected to be the second twin born, this can make vaginal delivery more complicated.
Birth defects
Twins are a little more likely than singleton pregnancies to have birth defects, although most twins do not. Twins that came from the same egg (monozygotic, or identical twins) are more likely to have birth defects than twins that came from separate eggs (dizygotic, or fraternal twins). Ultrasounds will be offered to assess for birth defects.
Special risks for pregnancies in which twins share a placenta (“monochorionic” twins)
In addition to the risks above, it’s possible for twins that share placentas to have issues with blood being moved from one twin to the other (twin-to-twin transfusion syndrome). There is also increased risk of one twin being particularly small (selective intrauterine growth restriction). For these reasons, twins that share a placenta are monitored with frequent ultrasound examinations, typically at least every two weeks starting at 16 weeks of pregnancy.
Risks to the mother
Twin pregnancies come with a higher risk of complications for the birthing person, such as:
Preeclampsia is a medical complication of pregnancy that usually presents with high blood pressure. It may also cause injury and may even be life-threatening. Your pregnancy provider will discuss preeclampsia warning signs and may recommend taking a low dose of aspirin every day to reduce the risk of preeclampsia.
Gestational diabetes is diabetes that may occur during pregnancy. Your pregnancy provider will screen you for diabetes, oftentimes early in pregnancy and again at 26 to 28 weeks of pregnancy.
Bleeding at birth (postpartum hemorrhage)
Bleeding at birth (postpartum hemorrhage) is another possible complication. The uterus muscle must contract after birth to stop bleeding, and because the uterus is stretched more in a twin pregnancy than a singleton pregnancy, there is a higher risk of bleeding after birth. Your delivery team will be monitoring bleeding carefully and will need to treat bleeding with medicines and other procedures.
Anemia (low levels of red blood cells)
Anemia is more common in twin pregnancies because the pregnant body is supplying nutrients to grow two fetuses. Your pregnancy provider may recommend additional iron supplementation or other nutrient supplementation to help build blood counts.
Postpartum depression is seen more in new parents of twins compared to parents of singleton pregnancies. Fortunately, postpartum depression is treatable, especially when recognized early.
Special care
People who are pregnant with twins should be cared for by pregnancy providers who are comfortable caring for twin pregnancies.
It is important to have an ultrasound early in pregnancy (usually sometime between 8 to 12 weeks) to determine whether the twins share a placenta to make sure that the appropriate monitoring is done.
Twin pregnancies have different weight gain recommendations than singleton pregnancies. For example, a person who starts pregnancy with a normal body weight is recommended to gain 37 to 54 pounds in a twin pregnancy, compared with 25 to 35 pounds in a singleton pregnancy. A nutritionist can help with healthy eating in a twin pregnancy.
Regular exercise is encouraged in twin pregnancies. Many people find more moderate exercises, such as walking and water aerobics, to be more comfortable with a growing twin pregnancy.
Like we do at Duke Health, your pregnancy care provider will develop a fetal well-being monitoring plan with you, customized for you and your pregnancy’s unique needs.
In addition to regular provider visits and the testing outlined above, twin pregnancies are typically followed with ultrasound checks for growth, often starting between 24-28 weeks. Your provider may recommend commencing regular antenatal testing, monitoring of fetal heartbeats (nonstress tests) or ultrasound checks of well-being (biophysical profiles) at some point in the late second or third trimesters. They will also help advise on the best delivery timing, and whether planning for a vaginal delivery is a safe option.
