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Summary The increases are quite widespread, affecting all age groups and all parts of the country.
The number of twins born in the United States has doubled in the last three decades largely as a result of fertility treatments, with one in 30 infants born in 2009 a twin, the Centers for Disease Control and Prevention said on Wednesday.The increases are quite widespread, affecting all age groups and all parts of the country, said Joyce Martin, a CDC epidemiologist and coauthor of the new study.
