title: Interpregnancy Intervals in the United States: Data From the Birth Certificate and the National Survey of Family Growth.
abstract: OBJECTIVE
  To describe data on interpregnancy intervals (IPI), defined as the timing between a live birth and conception of a subsequent live birth, from a subset of jurisdictions that adopted the 2003 revised birth certificate. Because this information is available among revised jurisdictions only, the national representativeness of IPI and related patterns to the entire United States were assessed using the 2006-2010 National Survey of Family Growth (NSFG).
  
  
  METHODS
  Birth certificate data are based on 100% of births registered in 36 states and the District of Columbia that adopted the 2003 revised birth certificate in 2011 (83% of 2011 U.S. births). The "Date of last live birth" item on the birth certificate was used to calculate months between the birth occurring in 2011 and the previous birth. These data were compared with pregnancy data from a nationally representative sample of women from the 2006-2010 NSFG.
  
  
  RESULTS
  Jurisdiction-specific median IPI ranged from 25 months (Idaho, Montana, North Dakota, South Dakota, Utah, and Wisconsin) to 32 months (California) using birth certificate data. Overall, the distribution of IPI from the birth certificate was similar to NSFG for IPI less than 18 months (30% and 29%), 18 to 59 months (50% and 52%), and 60 months or more (21% and 18%). Consistent patterns in IPI distribution by data source were seen by age at delivery, marital status, education, number of previous live births, and Hispanic origin and race, with the exception of differences in IPI of 60 months or more among non-Hispanic black women and women with a bachelor's degree or higher.
authors.affiliation: Division of Vital Statistics.
authors.forename: Casey E
authors.initials: CE
authors.lastname: Copen
authors.affiliation: Division of Vital Statistics.
authors.forename: Marie E
authors.initials: ME
authors.lastname: Thoma
authors.affiliation: Division of Vital Statistics.
authors.forename: Sharon
authors.initials: S
authors.lastname: Kirmeyer
mesh_terms: D000293:Adolescent; D000328:Adult; D001719:Birth Certificates; D001721:Birth Intervals / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate / Q000208:ethnology; D011795:Surveys and Questionnaires; D014481:United States; D014798:Vital Statistics; D055815:Young Adult