More American women than ever are having twins, triplets, quadruplets and even quintuplets, and it's not just because some are using fertility treatments, new research shows. READ: Mom's Survival Guide for Handling Twins, Triplets, and More Since the 1980s, the number of multiple births has jumped from roughly 20 sets per 1,000 live births to almost 35 sets per 1,000 live births, the study found. To determine whether this was attributable to more than just a surge in the avai