title: Estimating infertility prevalence in low-to-middle-income countries: an application of a current duration approach to Demographic and Health Survey data.
abstract: Can infertility prevalence be estimated using a current duration (CD) approach when applied to nationally representative Demographic and Health Survey (DHS) data collected routinely in low- or middle-income countries?
  
  
  
  Our analysis suggests that a CD approach applied to DHS data from Nigeria provides infertility prevalence estimates comparable to other smaller studies in the same region.
  
  
  
  Despite associations with serious negative health, social and economic outcomes, infertility in developing countries is a marginalized issue in sexual and reproductive health. Obtaining reliable, nationally representative prevalence estimates is critical to address the issue, but methodological and resource challenges have impeded this goal.
  
  
  
  This cross-sectional study was based on standard information available in the DHS core questionnaire and data sets, which are collected routinely among participating low-to-middle-income countries. Our research question was examined among women participating in the 2013 Nigeria DHS (n = 38 948). Among women eligible for the study, 98% were interviewed.
  
  
  
  We applied a CD approach (i.e. current length of time-at-risk of pregnancy) to estimate time-to-pregnancy (TTP) and 12-month infertility prevalence among women 'at risk' of pregnancy at the time of interview (n = 7063). Women who were 18-44 years old, married or cohabitating, sexually active within the past 4 weeks and not currently using contraception (and had not been sterilized) were included in the analysis. Estimates were based on parametric survival methods using bootstrap methods (500 bootstrap replicates) to obtain 95% CIs.
  
  
  
  The estimated median TTP among couples at risk of pregnancy was 5.1 months (95% CI: 4.2-6.3). The estimated percentage of infertile couples was 31.1% (95% CI: 27.9-34.7%)-consistent with other smaller studies from Nigeria. Primary infertility (17.4%, 95% CI: 12.9-23.8%) was substantially lower than secondary infertility (34.1%, 95% CI: 30.3-39.3%) in this population. Overall estimates for TTP >24 or >36 months dropped to 17.7% (95% CI: 15.7-20%) and 11.5% (95% CI: 10.2-13%), respectively. Subgroup analyses showed that estimates varied by age, coital frequency and fertility intentions, while being in a polygynous relationship showed minimal impact.
  
  
  
  The CD approach may be limited by assumptions on when exposure to risk of pregnancy began and methodologic assumptions required for estimation, which may be less accurate for particular subgroups or populations. Unrecognized pregnancies may have also biased our findings; however, we attempted to address this in our exclusion criteria. Limiting to married/cohabiting couples may have excluded women who are no longer in a relationship after being blamed for infertility. Although probably rare in this setting, we lack information on couples undergoing infertility treatment. Like other TTP measurement approaches, pregnancies resulting from contraceptive failure are not included, which may bias estimates.
  
  
  
  Nationally representative estimates of TTP and infertility based on a clinical definition of 12 months have been limited within developing countries. This approach represents a pragmatic advance in our ability to measure and monitor infertility in the developing world, with potentially far-reaching implications for policies and programs intended to address reproductive health.
  
  
  
  There are no competing interests and no financial support was provided for this study. Financial support for Open Access publication was provided by the World Health Organization.
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA.|Guttmacher Institute, 125 Maiden Lane, 7th Floor, New York, NY 10038, USA.
authors.forename: Chelsea B
authors.initials: CB
authors.lastname: Polis
authors.affiliation: Department of Public Health,St. Catherine University, 2004 Randolph Ave., St. Paul, MN 55105, USA.
authors.forename: Carie M
authors.initials: CM
authors.lastname: Cox
authors.affiliation: Department of Reproductive Health and Research including UNDP/UNFPA/UNICEF/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), World Health Organization, Geneva, Switzerland.
authors.forename: Özge
authors.initials: Ö
authors.lastname: Tunçalp
authors.affiliation: Department of Epidemiology and Biostatistics,University of South Carolina, 915 Greene Street, Columbia, SC 29208, USA.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: McLain
authors.affiliation: Department of Family Science,University of Maryland, 4200 Valley Drive, College Park, MD 20742, USA.
authors.forename: Marie E
authors.initials: ME
authors.lastname: Thoma
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D003906:Developing Countries; D005260:Female; D006306:Health Surveys; D006801:Humans; D007246:Infertility / Q000453:epidemiology*; D009549:Nigeria / Q000453:epidemiology; D011247:Pregnancy; D015995:Prevalence; D061685:Time-to-Pregnancy; D055815:Young Adult
keywords: current duration; developing countries; infertility; survival analysis; time-to-pregnancy