Number of U.S. Twin Births Has Doubled Since 1980

The number of twins born in the United States has risen by 76 percent from 1980 to 2009, recent figures by the CDC´s National Center for Health Statistics indicate.

Researchers say this is mostly due to the increased use of fertility treatments, such as ovulation stimulation drugs.

The study by Dr. Joyce Martin, MPH, also suggests that twin births are riskier than single births as mothers of twins are more likely to suffer from complications during the pregnancy.