Purpose <p>Night-to-night adherence to sleep-disordered breathing (SDB) treatment with either continuous positive airway pressure (CPAP) or mandibular advancement splints (MAS) in pregnancy has not been well characterized. The objective of this study was to assess night-to-night adherence patterns from existing CPAP and MAS data in pregnancy.</p> Methods <p>Three separate pregnancy cohorts evaluating treatment for SDB in the second and third trimester were used: 1) CPAP in gestational diabetes mellitus (GDM), 2) CPAP in hypertensive disorders of pregnancy (HDP), and 3) mandibular advancement splints (MAS). The first 30 days of objective adherence data obtained from CPAP and MAS devices were used in this descriptive analysis.</p> Results <p>Data from 37 CPAP users and 15 MAS users was analyzed. For the GDM and HDP cohorts, three patterns of adherence were observed: 1) consistent CPAP users (38%), 2) improved CPAP usage after initial adaptation (16%), and 3) inconsistent CPAP users (46%). For the MAS cohort, the three observed patterns of adherence were: 1) consistent MAS users (47%), 2) initial usage with subsequent decrease in adherence (20%), and 3) inconsistent MAS users (33%). Participant characteristics (demographics, disease severity) were similar between adherence groups, with the exception of longer total sleep time in consistent CPAP users of the GDM cohort and greater gestational age in consistent CPAP users of the HDP cohort.</p> Conclusion <p>Overall, objective night-to-night adherence patterns revealed that almost half of CPAP and MAS users had difficulty adapting to treatment in the first 30 days of treatment. Early usage patterns in pregnancy may provide insight into identifying patients who are at risk for poor adherence and for developing tailored and timely interventions to enhance adherence to therapy.</p> Trial registration <p>ClinicalTrials.gov Identifiers: NCT02245659, NCT03309826, NCT03138291</p>