A multiple pregnancy is when a woman is pregnant with two or more fetuses. Twins are the most common type of multiple pregnancy. So-called “higher-order” pregnancies (when a woman is carrying triplets, quadruplets, quintuplets, or more) are less common.

The risk for certain complications during and after pregnancy is higher in multiple pregnancies. To lessen these risks your doctor will see you more often than a woman carrying one baby.

Twins in Utero
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Multiple pregnancies occur when a single fertilized egg divides and develops into two or more fetuses (identical twins) or when more than one egg is fertilized by a different sperm (fraternal twins). Triplets, quadruplets, and quintuplets can be identical, fraternal, or a combination of both.