United States

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Location: United States
Topic: Late preterm by maternal age
Format: Bar Graph
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Late preterm by maternal age: United States, 2013-2015 Average

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• Maternal age is a risk factor for preterm birth, with higher preterm birth rates found among the youngest and oldest mothers in the U.S. 
• During 2013-2015 (average) in the United States, late preterm birth rates were highest for women ages 40 and older (9.9%), followed by women ages 30-39 (7.1%), under age 20 (6.9%) and ages 20-29 (6.5%). 
• Of all infants born during 2013-2015 (average), 6.4% were to mothers under the age of 20, 50.8% were to mothers ages 20-29 years, 39.8% were to mothers ages 30-39 years, and 3.0% were to mothers ages 40 and older. 


  • Late preterm is between 34 and 36 weeks gestation.


  • National Center for Health Statistics, final natality data.
  • Retrieved December 14, 2018, from www.marchofdimes.org/peristats.