| ||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 2012-2014 (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 2012-2014 (average), 7.1% were to mothers under the age of 20, 51.3% were to mothers ages 20-29 years, 38.7% were to mothers ages 30-39 years, and 3.0% were to mothers ages 40 and older. |
National Center for Health Statistics, final natality data.
Retrieved March 23, 2017, from www.marchofdimes.org/peristats.