Purpose: Describe patient characteristics, pregnancy outcomes, and infant outcomes among pregnant patients and their linked infants in the novel Maternal Outcomes Masterset (MOM). Methods: We used closed claims within the MOM data to identify publicly and privately-insured patients at first record of pregnancy 1/1/2018-12/1/2021 with ≥180 days baseline enrollment. We described characteristics during baseline and follow-up (until an observed pregnancy endpoint, disenrollment, or 42-week maximum). We described maternal and infant characteristics overall and by infant linkage. Results: Among 1,438,861 pregnant patients meeting the study criteria, the most common pregnancy endpoint recorded was live birth (42%) followed by spontaneous abortion (14%). Among 602,721 patients with a live birth, 99% had a week-specific gestational age recorded and 35% had at least one linked infant. Patients with infant linkage and sufficient follow-up (N=155,621) had similar baseline comorbidities, pregnancy complications, and gestational age at delivery versus those without any linkage. However, more patients with linkage had commercial coverage (70% vs 31%), and were therefore older (50% vs 31% aged ≥30 years) and more likely to have unknown race (57% vs 34%). Conclusions: In this large sample of pregnant patients, maternal and infant characteristics generally align with national statistics, providing confidence in the use of this novel data source for pregnancy research. Further, confirmation that the subset of patients with infant linkage is similar to the overall pregnancy cohort provides assurance that this subset can be considered representative.