Preterm Birth in Birth Outcomes: Measures and Data
What is the public health burden of preterm births?Preterm infants are more likely than term infants to experience respiratory distress, infection, central nervous system complications, feeding difficulties, and slow weight gain. Preterm birth and low birth weight combined are the second leading cause of infant mortality in the U.S., and the leading cause of mortality among black infants under 1 year. In 2008, 9.0% of singleton (one baby) births in Washington were preterm.
Some populations in Washington have a higher risk of preterm birth than others. From 2006-2008, 16.3% of American Indian and Alaska Native babies were born preterm compared to 12.9% non-Hispanic (NH) African American babies, 11.3% Hispanic babies, 10.7% NH American Pacific Island babies, and 9.9% NH Caucasian babies. The Maternal and Child Health Data Report and the Perinatal Indicators Report for Washington Residents provide more detailed statistics on these trends. See the Health of Washington State to explore the relationship between preterm birth rates, low birth weight, income, education and other socioeconomic factors.
Although the causes of preterm birth are not well understood, preterm delivery is clearly associated with maternal age younger than 18 or older than 40, smoking, alcohol use, perinatal infection, and a number of other risk factors (discussed under Basic Facts for Preterm Birth).
Some environmental exposures may influence risk for preterm birth. Some researchers are exploring the relationship between exposures to a variety of contaminants and preterm birth, including air pollution, but results remain inconclusive. WTN maintains a list of recent publications that discuss the scientific evidence concerning the impact of environmental hazards on an array of birth outcomes, including preterm birth.
How is preterm birth defined and tracked?The preterm birth rate is calculated by dividing all live births born before 37 weeks gestation by the total number of live births in the same time period, and multiplying by 100. Preterm births can be classified into 3 groups: "preterm" (live births under 37 weeks), "moderately preterm" (live births between 32-36 weeks), and "very preterm" (live births less than 32 weeks).
In Washington, the Department of Health (DOH) Center for Health Statistics tracks birth through the Vital Registration System. The State Registrar reports birth data to CDC National Center for Health Statistics, which maintains files on all births in the United States and its territories. Data are standardized among all jurisdictions and are generally available one year later than state data.
What is being done to reduce the rate of preterm birth? In Washington, DOH and Department of Social and Health Services (DSHS) work with a variety of partners in the state to carry out programs to prevent low birth weight, preterm birth, and promote healthy pregnancies, including:
These services address issues that promote healthy birth outcomes such as prevention of unintended pregnancy, healthy birth spacing, prenatal medical care access, smoking cessation, alcohol and drug use prevention, healthy weight gain, and addressing family violence.
- State Title X Family Planning Program: family planning and women’s health services
- Special Supplemental Nutrition Program for Women, Infants and Children (WIC): breastfeeding support, nutritious foods, education and referrals to preventive services
- First Steps Program: prenatal medical care, Maternity Support Services, Infant Case Management
- Take Charge Program: family planning services for low income men and women
Other Department of Health activities include data surveillance, perinatal quality improvement projects, and development and dissemination of preconception healthy living messages.
More Information on Specific Birth Outcomes