BackgroundThe birthweight of a newborn is critical to their health, development, and well‐being. Previous studies that used maternal characteristics to predict birthweight did not employ a harmonised scale to assess the risk of low birthweight (LBW).ObjectiveThe goal of this study was to develop a new instrument that uses items on a uniform scale to assess the risk of an LBW in a pregnant woman.MethodsItem response theory was employed to evaluate a similar existing scale, and some weaknesses were identified.ResultsBased on the observed weaknesses of the existing scale, a new uniform scale was developed, which is a 3‐point Likert scale consisting of seven items.ConclusionThe scale, termed birthweight questionnaire, is a valuable tool for collecting data that could assist in assessing the risk of an LBW at every stage of pregnancy.