| ||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 2008-2010 (average) in San Francisco, late preterm birth rates were highest for women ages 40 and older (9.4%), followed by women under age 20 (7.0%), ages 30-39 (6.8%) and ages 20-29 (6.4%). |
| ||Of all infants born during 2008-2010 (average), 3.0% were to mothers under the age of 20, 27.6% were to mothers ages 20-29 years, 61.5% were to mothers ages 30-39 years, and 7.9% were to mothers ages 40 and older. |
National Center for Health Statistics, final natality data.
Retrieved May 25, 2013, from www.marchofdimes.com/peristats.