Twins are born at a rate of just over 33 twins for every 1,000 live births, according to the Centers for Disease Control and Prevention. For 2012, the CDC reported a total of 131,269 twin births in the United States.
There has been a 76 percent increase in the rate of twin births from 1980 to 2012. According to WebMD, the primary reason for this increase is the more frequent use of fertility treatments, including in-vitro fertilization and ovulation stimulation medications. WebMD further states that women are embracing motherhood at an older age, which also contributes to an increase in twin births.