Indonesia Demographic and Health Survey

Birth interval was used as a proxy for the conceptually preferable interpregnancy interval because the IDHS does not collect conception dates or last menstrual period information, potentially biasing shorter-interval associations. The analytic sample was restricted to 17,171 women with at least one pregnancy in the five years preceding the survey, from an eligible pool of 49,627 women aged 15–49. The study used reproductive calendar data from the 2017 IDHS, a nationally representative household survey employing a two-stage stratified cluster sampling design.