Background: Existing approaches to measuring women's pregnancy intentions suffer important limitations, including retrospective assessment, overly simple categories, and a presumption that all women plan pregnancies. No psychometrically valid scales exist to prospectively measure the ranges of women's pregnancy preferences., Materials and Methods: Using a rigorous construct modeling approach, we developed a scale to measure desire to avoid pregnancy. We developed 60 draft items from existing research, assessed comprehension through 25 cognitive interviews, and administered items in surveys with 594 nonpregnant women in 7 primary and reproductive health care facilities in Arizona, New Jersey, New Mexico, South Carolina, and Texas in 2016-2017. We used item response theory to reduce the item set and assess the scale's reliability, internal structure validity, and external validity. Items were included based on fit to a random effects multinomial logistic regression model (partial credit item response model), correspondence of item difficulty with participants' pregnancy preference levels, and consistency of each item's response options with overall scale scores., Results: The 14 final items covered 3 conceptual domains: cognitive preferences, affective feelings, and practical consequences. Items fit the unidimensional model, with a separation reliability of 0.90 (Cronbach α: 0.95). The scale met established criteria for internal validity, including correspondence between each item's response categories and overall scale scores. We found no important differential item functioning by participant characteristics., Conclusions: A robust measure is available to prospectively measure desire to avoid pregnancy. The measure can aid in identifying women who could benefit from contraceptive care and research on less desired pregnancy.