More twins are being born these days than ever before.

More women in the U.S. are giving birth to twins. In fact, one out of 30 babies in 2009 was a twin (, compared with only one in 55 in 1980. experts say the increase in twin births is due to the fact that many women are waiting until their 30s to get pregnant. Women in their 30s are more likely than younger or older women to give birth to twins.

Having twins is also, of course, linked to an increase in fertility drugs and in-vitro fertilization, which often produces multiples. Doctors warn that the increase in twins could be a negative thing. Twins are often born premature, and twin births can be dangerous for both the babies and the mother.