Isotemporal Associations of Patterns and Domains of Sedentary Behavior and Physical Activity with Sleep Quality in Pregnant Women in Saudi Arabia

<b>Background:</b> Although higher sedentary behavior (SB) and lower physical activity (PA) have been associated with poor prenatal sleep quality, the influence of specific exchanges of SB and types of PA on sleep quality during pregnancy remains unexplored. <b>Objectives:</b> This secondary, cross-sectional analysis examined associations between the statistical replacement of patterns (weekdays, weekends) and domains (leisure, occupational, commuting) of SB with moderate (MPA), vigorous (VPA), or moderate-to-vigorous (MVPA) PA and sleep quality among pregnant women in Saudi Arabia. <b>Methods:</b> Participants (n = 935; age = 30 ± 5.6 years; first trimester = 24.1%, second trimester = 33.9%, third trimester = 42.0%) self-reported their patterns and domains of SB, PA, and sleep quality using validated instruments. Adjusted isotemporal substitution models evaluated the associations of exchanging 30 min of different SB and PA with sleep quality. <b>Results:</b> Replacing 30 min of total or leisure SB on weekdays with 30 min of MPA was associated with improved sleep quality (β = -0.519 and -0.590, respectively; <i>p</i> < 0.05) only among those in their first trimester. Paradoxically, replacing 30 min of total, leisure, occupational, or commuting SB across the week, on weekdays, and weekends with 30 min of VPA was associated with poor prenatal sleep quality (β ranged between 1.258 and 7.217; <i>p</i> < 0.05 for all). Exchanging SB with MPVA or different domain-specific SB did not influence sleep quality (<i>p</i> > 0.05 for all). <b>Conclusions:</b> These novel findings suggest that although replacing SB with PA may help enhance sleep quality in pregnant women, particularly during the first trimester, the underlying associations are likely multifaceted. The variable relationships observed emphasize the importance of considering patterns and domains of SB and intensity of PA used as a replacement, rather than total duration solely, to improve prenatal sleep quality, especially during early pregnancy, particularly in Saudi Arabia.