Background: Parent-clinician shared decision making is the recommended model for the care of premature infants; thus, clinicians provide prenatal prematurity counseling to parents in the event of a mother's hospitalization for premature birth. However, parental understanding of medical jargon commonly used during prematurity counseling is unknown. Methods: Within an overall research agenda to develop and test an educational aid for prenatal prematurity education, we designed the Parental Knowledge of Premature Birth questionnaire. To evaluate parental comprehension of the medical jargon contained within the questionnaire, we conducted cognitive interviews, a formal method for evaluating comprehension and response to questionnaire items. Parents were recruited from a Level IV Neonatal Intensive Care Unit; purposeful recruitment ensured diversity with respect to gender, race, literacy level, and child's gestational age. Data collection and analysis followed standard qualitative methods for cognitive interviewing. We report on the insights gained from these cognitive interviews regarding parental understanding of crucial medical jargon commonly used during prenatal prematurity counseling. Results: Participants included 10 women and 6 men who ranged in age from 23 to 38 years and represented Black/African-American (38%), Asian (6%), and white (56%) backgrounds. Five participants (31%) had less than a high school education or reading level below 9th grade (Wide Range Achievement Test version 4 reading subtest). In the first round of interviews, parents of all education and literacy levels had difficulty with medical jargon commonly used in prematurity counseling. Terms that parents found difficult to understand included "gestational age", "mild or no developmental problems", and "neonatologist". Modified terms tested in a second round of interviews showed improved comprehension. Conclusion: Cognitive interviews provided empirical testing of parental understanding of crucial medical jargon and highlighted that language commonly used during prenatal prematurity counseling is not understood by many parents. For parents to participate in shared decision making, plain language should be used to maximize their understanding of medical information.