Twin birth rate hits new high

NEW YORK (AP) — The number of twins being born in the U.S. is at an all-time high, but birth rates of other multiples are at their lowest in two decades.

Of the nearly 4 million babies born last year, more than 135,000 were twins. That's about 1 in every 29 babies. In 1980, only 1 in every 53 babies was a twin.

Why the twin increase? More women are waiting until they are older to have babies, and mothers in their 30s are more likely to have twins than younger women.

On the other hand, doctors have been implanting fewer embryos during in vitro fertilization than in the past, in recognition that more embryos increase the risk of dangerous complications. Experts say the rate of triplet and higher-order births has fallen 40 percent from its 1998 peak.