Sow welfare across the reproductive cycle encompasses gestation, farrowing, lactation, and weaning - each with distinct welfare challenges. Gestating sows in group housing face social competition for feed and resting space, causing injuries and welfare stress in poorly managed systems. Electronic sow feeding (ESF) systems enable individual feeding in group housing, reducing competition. Lameness - affecting 15-30% of sows - is a primary welfare concern and leading cause of culling. Sow longevity is a key welfare indicator: modern sows average 2.5-3 parities before culling compared to a biological potential of 5-7. Premature culling represents both welfare failure and economic loss. Stockperson attitude and care quality are primary determinants of sow welfare outcomes in any housing system. Research identifies low culling rates, high farrowing rates, good body condition, and low lameness prevalence as markers of high-welfare sow management. EU transition away from gestation crates requires demonstration that group housing can deliver equivalent or better welfare.