Products - Data Briefs - Number 39 - May 2010

NCHS Data Brief
Number 39, May 2010

Are Preterm Births on the Decline in the United States?
Recent Data From the National Vital Statistics System

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http://www.cdc.gov/nchs/data/databriefs/db39.pdf

Joyce A. Martin, M.P.H.; Michelle J.K. Osterman, M.H.S.; and Paul D. Sutton, Ph.D.

Key findings
•Following a long period of fairly steady increase, the U.S. preterm birth rate declined for the second straight year in 2008 to 12.3 percent, from 12.8 percent in 2006.
•This marks the first 2-year decline in the preterm birth rate in nearly three decades.
•Preterm birth rates declined from 2006 to 2008 for mothers of all age groups under age 40, for the three largest race and Hispanic origin groups and for most U.S. states.
•The percentage of preterm births was down for all types of deliveries from 2006 to 2008, for cesareans and for induced and noninduced vaginal deliveries.
The U.S. preterm birth rate (less than 37 weeks of gestation) rose by more than one-third from the early 1980s through 2006 (1). This rise has been a cause of great concern (2,3). Preterm infants are at increased risk of life-long disability and early death compared with infants born later in pregnancy (2,4).

Many reasons, such as changes in maternal demographics and increases in multiple births, have been suggested for the growth in preterm births (5). Another factor cited is the heightened use of obstetric interventions such as induction of labor and cesarean delivery earlier in pregnancy (5,6,7). Although it is not possible to know whether an infant would be born preterm if labor was not induced or delivered by cesarean, studies suggest that increased use of these procedures before 37 completed weeks of gestation may have influenced the upswing in preterm birth rates (6,7).

Preliminary 2007 and 2008 birth certificate data reveal a shift in the long upward trend in preterm births (8,9). This report describes this change.

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Products - Data Briefs - Number 39 - May 2010