Sow housing systems have always focused on efficient utilization of space. Housing design affects the welfare status of sows at any stage of growth or production. The restriction placed on freedom of movement of pregnant sows has been a major welfare criticism leveled at individual stall housing. While it is presented as one of the main criteria for evaluating the welfare of animals, freedom of movement is arguably the most controversial design criterion for housing systems. The limited space in stalls is reported to reduce the ease with which the sow can change posture, and can cause injury and discomfort. It is important to note that the adequacy of space allowance depends on space available relative to the size of the pig. Depriving animals of opportunities to walk and turn around may affect their health, performance, and overall welfare. Most of the commercially available stalls provide the minimum space required for average sized sows and have similar design and measurements. The size of sows, nevertheless, varies considerably, depending on age, genetics, feeding level, and stage of gestation, and effective space available to a sow may become inadequate with advancement of pregnancy. Also, the welfare status of sows may not be static throughout their stay in the gestation housing system. Factors such as: separation from piglets, change in accommodation, and restricted feeding may contribute to an initially low welfare status of sows in stalls. The sow may adjust to the situation as the stay continues. In late gestation, the sow may be compromised by the relatively smaller space available with increasing body size. Stress associated with advanced gestation may cause further compromise. Though confinement in stalls has been viewed as adversely affecting welfare, the manner in which the compromise in welfare progresses during the course of the stay in the stalls has not been studied in detail. The present study, therefore, aimed to assess the welfare status of sows housed in stalls through measurement of injury scores, salivary cortisol concentrations, and behavior during the initial (day 5), middle (day 56) and late (day 108) stages of gestation. Timelapse video recording for 24-hour periods was used to observe their behavior on each day. Salivary cortisol concentrations were assessed using adioimmunoassay. Injuries were scored individually and added to provide a total injury score (TIS). It was concluded that Cortisol concentrations were lower on gestation day 56 than on other days, and TIS was higher on day 108 than on days 5 and 56. Time spent lying was highest on day 108. Sows spent more time on exploration and active behavior on day 56 than on days 5 and 108. Time for the transition from sitting to lying was higher on day 108 than on day 56. Frequencies of overall postural change and of standing or sitting to lying and lying to sitting were highest on day 5. Frequency of lying to standing was higher on day 5 than on day 108. Body weight was negatively correlated with time spent on exploration and active behavior and standing, and positively correlated with time spent lying. Therefore, the welfare of sows in gestation stalls appears to be more compromised during early and late stages of gestation. Providing larger sows with larger stalls might improve welfare.