The rate of triplet and other higher-order multiple births increased substantially,from 37 per 100000 live births in 1980 to 194 in 1998, a trend largely attributable to increased usage of fertility therapies.
During 1999-2003, and the rate of triplet and higher-order multiple births has remained steady. Older mothers and non-Hispanic white mothers are the most likely to fill a triplet or higher-order multiple birth.
Source: cdc.gov