ATLANTA -- The number of twins born in the U.S. soared over the last three decades, mostly the result of test-tube babies and women waiting to have children until their 30s, when the chances of twins increase.
In 2009, 1 in 30 babies born in the U.S. was a twin, an astounding increase over the 1-in-53 rate in 1980, according to a government report issued Wednesday.
"When people say it seems like you see more twins nowadays, they're right," said Joyce Martin, an epidemiologist who co-authored the report by the Centers for Disease Control and Prevention.
Some increase was expected, as more women are delaying starting a family until they are over 30. For some unknown reason, mothers in their 30s are more likely to have twins than younger or older women. Up to a third of the increase can be attributed to that, Martin said.
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The rest of the rise is due to fertility drugs and treatments.
"You have a double whammy going on. There are more older moms and more widespread use of fertility-enhancing therapies," Martin said.