title: Measuring infertility in populations: constructing a standard definition for use with demographic and reproductive health surveys.
abstract: BACKGROUND
  Infertility is a significant disability, yet there are no reliable estimates of its global prevalence. Studies on infertility prevalence define the condition inconsistently, rendering the comparison of studies or quantitative summaries of the literature difficult. This study analyzed key components of infertility to develop a definition that can be consistently applied to globally available household survey data.
  
  
  METHODS
  We proposed a standard definition of infertility and used it to generate prevalence estimates using 53 Demographic and Health Surveys (DHS). The analysis was restricted to the subset of DHS that contained detailed fertility information collected through the reproductive health calendar. We performed sensitivity analyses for key components of the definition and used these to inform our recommendations for each element of the definition.
  
  
  RESULTS
  Exposure type (couple status, contraceptive use, and intent), exposure time, and outcomes were key elements of the definition that we proposed. Our definition produced estimates that ranged from 0.6% to 3.4% for primary infertility and 8.7% to 32.6% for secondary infertility. Our sensitivity analyses showed that using an exposure measure of five years is less likely to misclassify fertile unions as infertile. Additionally, using a current, rather than continuous, measure of contraceptive use over five years resulted in a median relative error in secondary infertility of 20.7% (interquartile range of relative error [IQR]: 12.6%-26.9%), while not incorporating intent produced a corresponding error in secondary infertility of 58.2% (IQR: 44.3%-67.9%).
  
  
  CONCLUSIONS
  In order to estimate the global burden of infertility, prevalence estimates using a consistent definition need to be generated. Our analysis provided a recommended definition that could be applied to widely available global household data. We also summarized potential biases that should be considered when making estimates of infertility prevalence using household survey data.
authors.affiliation: Department of Health Statistics and Informatics, World Health Organization, Geneva, Switzerland. stevensg@who.int.
authors.forename: Maya N
authors.initials: MN
authors.lastname: Mascarenhas
authors.forename: Hoiwan
authors.initials: H
authors.lastname: Cheung
authors.forename: Colin D
authors.initials: CD
authors.lastname: Mathers
authors.forename: Gretchen A
authors.initials: GA
authors.lastname: Stevens