PRETERM BIRTHS

This indicator reports the percentage of total annual births which are preterm. Preterm birth is defined as the delivery of an infant at less than 37 weeks of gestation, the period of time between conception and birth. Late preterm births (occurring between 34 to 36 weeks of gestation), moderate preterm births (occurring between 32 to 33 weeks of gestation) and very preterm births (occurring less than 32 weeks of gestation) are subsets of preterm births. Since 2014, preterm births have been calculated by establishing the gestational age based on the obstetric estimate. For years 2013 and earlier, the gestational age was calculated in the month prenatal care began by recording the date of the last normal menses. This change may lead to a slight discontinuity in preterm birth results between years 2013 and 2014.

Preterm birth is an important public health issue requiring sustained focus on its causes, consequences and prevention strategies.1 Several factors – economic, personal, medical and behavioral – may increase the likelihood that a woman has preterm labor and delivers early.2 Preterm infants are at risk of lifelong neurologic, cognitive and behavioral problems.3,4 Preterm births and low birth weight are often, but not always, associated. In the United States, the preterm birth rate increased slightly from 2014, to 9.6% in 2015, as did the rate of low birthweight (8.07% in 2015).5 Preterm births cost the U.S. health care system more than $26 billion each year.6

• Preterm births accounted for 7.6% of the 37,621 births to Orange County residents in 2015, dropping 19.2% from 9.4% in 2006. By comparison, the rate for the United States was higher at 9.6% (25% decrease since 2006) in 2015.

• Disparities persist with preterm births among Black infants at 10.8%, followed by Hispanic (8.0%), White (7.3%) and Asian (7.0%) infants (the percentages decreased for all race/ ethnicities, compared to 2006).

• Out of all preterm births, the percentage of preterm births was highest among women less than 19 years old (14.1%), followed by women older than 40 years (13.5%), 35 to 39 years (9.7%), 30 to 34 years (8.7%), 20 to 24 years (8.3%), and 25 to 29 years (7.6%) of age.

Note: Percent of preterm births in California is no longer available in 2015. Percent calculated from number of births with known obstetric estimate gestational age less than 37 weeks for 2014. Rates prior to 2014 were calculated from last menstrual cycle dates. Sources:

Note: Percent calculated from number of births with known obstetric estimate gestational age less than 37 weeks for 2014. Rates prior to 2014 were calculated from last menstrual cycle dates. Source:

Note: N/A indicates no data are available. Laguna Woods rate is based on fewer than five births. Rates based on less than five events are unstable and should be interpreted with caution. Source: