Studies measuring stress by the occurrence of life events or anxiety during pregnancy have produced inconsistent findings about the impact of prenatal maternal stress on birth outcomes. More robust approaches conceptualize and measure prenatal stress as the confluence of conditions or events (stimuli), appraisals of these, and resulting emotions (responses). These approaches are improved by including pregnancy-specific stress, which results from women’s appraisals and responses to the specific aspects of pregnancy that they find stressful. Pregnancy-specific stress has been shown to be a particularly harmful type of stress, predicting poorer maternal health, unhealthy behaviors, and adverse birth outcomes. The Prenatal Distress Questionnaire (PDQ) and its successor, the NuPDQ, are well-tested instruments that measure pregnancy-specific stress with strong reliability and validity. Using these instruments to assess pregnancy-specific stress enhances our ability to identify and quantify the difficulties faced by pregnant women and can help us provide the supports and resources that promote healthy birth outcomes.