title: Breastfeeding rates differ significantly by method used: a cause for concern for public health measurement.
abstract: OBJECTIVE
  Accurate measurements of prevalence of "any" breastfeeding and "exclusive" breastfeeding help assess progress toward public health goals. We compared two commonly used data sources for measuring breastfeeding rates to assess agreement.
  
  
  METHODS
  The National Immunization Survey (NIS) is used by the Centers for Disease Control and Prevention to measure progress toward national breastfeeding goals and obtains breastfeeding outcomes retrospectively at 19-35 months. The California Newborn Screen (CNS) is a contemporaneous measure of breastfeeding during birth hospitalization and measures progress toward public health goals in California. We compared results for "any breastfeeding" and "exclusive breastfeeding" for California infants in the NIS to those in the CNS using descriptive statistics.
  
  
  RESULTS
  Our results show that the two methods produce similar results for "any" breastfeeding at <4 days: 82.7%, 95% confidence interval (79.6%, 85.8%) in the NIS and 86.1% (86.0%, 86.2%) in the CNS. However, the two methods produce very different results for "exclusive" breastfeeding at <4 days: 60.4% (56.6%, 64.1%) in the NIS and 41.6% (41.5%, 41.7%) in the CNS. Rates of "exclusive" breastfeeding varied more for some subgroups; for Hispanics, estimates were 61.1% (56.1%, 66.1%) in the NIS and 29.7% (29.5%, 29.9%) in the CNS.
  
  
  CONCLUSIONS
  There is good agreement between two disparate methods for assessing "any" breastfeeding rates. However, our findings suggest that the NIS, the CNS, or both are flawed measures of "exclusive" breastfeeding. Validated methods for measuring "exclusive" breastfeeding would allow improved monitoring of breastfeeding prevalence.
authors.affiliation: Department of Pediatrics, University of California San Francisco, 94143-0503, USA. FlahermanV@peds.ucsf.edu
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Flaherman
authors.forename: Alyna T
authors.initials: AT
authors.lastname: Chien
authors.forename: Charles E
authors.initials: CE
authors.lastname: McCulloch
authors.forename: R Adams
authors.initials: RA
authors.lastname: Dudley
mesh_terms: D000328:Adult; D001942:Breast Feeding / Q000453:epidemiology / Q000706:statistics & numerical data*; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011159:Population Surveillance; D015995:Prevalence; D011634:Public Health / Q000379:methods / Q000706:statistics & numerical data*