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Complications of Multiple Pregnancy

Why is multiple pregnancy a concern?

Being pregnant with more than one baby is exciting and is often a happy event for many couples. However, multiple pregnancy has increased risks for complications. The most common complications include the following:

  • Preterm labor and birth
    Over 60 percent of twins and nearly all higher-order multiples are premature (born before 37 weeks). The higher the number of fetuses in the pregnancy, the greater the risk for early birth. Premature babies are born before their bodies and organ systems have completely matured. These babies are often small, with low birthweights (less than 2,500 grams or 5.5 pounds), and they may need help breathing, eating, fighting infection, and staying warm. Very premature babies, those born before 28 weeks, are especially vulnerable. Many of their organs may not be ready for life outside the mother's uterus and may be too immature to function well. Many multiple birth babies will need care in a neonatal intensive care unit (NICU).

  • Gestational hypertension
    Women with multiple fetuses are two to five times more likely to develop high blood pressure of pregnancy. This condition often develops earlier and is more severe than pregnancy with one baby. High blood pressure can increase the chance of placental abruption (early detachment of the placenta).

  • Anemia
    Anemia is more common in multiple pregnancies than in a single birth.

  • Birth defects
    Multiple birth babies have a higher risk of congenital (present at birth) abnormalities including neural tube defects (such as spina bifida), gastrointestinal, and heart abnormalities.

  • Miscarriage
    A phenomenon called the vanishing twin syndrome in which more than one fetus is diagnosed, but one vanishes (or is miscarried), usually in the first trimester, may occur in a multiple pregnancy. This may or may not be accompanied by bleeding. The risk of pregnancy loss is increased in later trimesters as well.

  • Twin-to-twin transfusion syndrome
    Twin-to-twin transfusion syndrome (TTTS) is a condition of the placenta that develops only with identical twins that share a placenta. Blood vessels connect within the placenta and divert blood from one fetus to the other. It occurs in about 10 percent of twins with a shared placenta.


    In TTTS, blood is shunted from one fetus to the other through blood vessel connections in a shared placenta. Over time, the recipient fetus receives too much blood, which can overload the cardiovascular system and cause too much amniotic fluid to develop. The smaller donor fetus does not get enough blood and has low amounts of amniotic fluid.

Illustration of a twin birth, twin to twin transfusion
Click Image to Enlarge

  • Abnormal amounts of amniotic fluid
    Polyhydramnios (too much fluid) and oligohydramnios (too little fluid) are more common in multiple pregnancies, especially for twins that share a placenta.

  • Cesarean delivery
    Abnormal fetal positions increase the chances of cesarean birth.

  • Postpartum hemorrhage
    The large placental area and over-distended uterus place a mother at risk for bleeding after delivery in many multiple pregnancies.

What is multifetal pregnancy reduction?

In recent years, a procedure called multifetal pregnancy reduction has been used for very high numbers of fetuses, typically three or more. This procedure involves injecting one or more fetuses with a lethal medication, causing fetal death. The objective of multifetal reduction is that by reducing the number of fetuses in the pregnancy, the remaining fetuses may have a better chance for health and survival. Consult your physician for additional information.