Being pregnant with more than 1 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% 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 more than twice as likely to develop high blood pressure of pregnancy. This condition often develops earlier and is more severe than pregnancy with one baby. It can also increase the chance of placental abruption (early detachment of the placenta).
Anemia. Anemia is more than twice as common in multiple pregnancies as in a single birth.
Birth defects. Multiple birth babies have about twice the risk of congenital (present at birth) abnormalities including neural tube defects (like spina bifida), gastrointestinal, and heart abnormalities.
Miscarriage. A phenomenon called the vanishing twin syndrome in which more than 1 fetus is diagnosed, but vanishes (or is miscarried), usually in the first trimester, is more likely in multiple pregnancies. 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 happens in about 15% of twins with a shared placenta.In TTTS, blood is shunted from 1 fetus to the other through blood vessel connections in a shared placenta. Over time, the recipient fetus receives too much blood. This 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. TTTS can be treated during pregnancy by withdrawing some of the extra fluid with a needle or with surgery on the placenta. Sometimes, the twins may need to be delivered early.
Abnormal amounts of amniotic fluid. Amniotic fluid abnormalities are more common in multiple pregnancies, especially for twins that share a placenta.
Cord entanglement. Cord entanglement for the twins that share amniotic sac. In these cases, monitoring of the fetuses often in the third trimester may be necessary.
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.
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