A multiple pregnancy is the presence of two or more fetuses growing in the uterus. A pregnancy of twins or more is considered high-risk because complications and premature birth are more common than in pregnancies of one fetus.
Many women have healthy multiple pregnancies and healthy babies. But the risk of serious problems increases with each extra baby you carry at the same time. These problems include preeclampsia, gestational diabetes, miscarriage, and premature (preterm) birth. Preterm birth increases the babies' risk of serious lung, brain, heart, and eye problems.