Myth: The Type of Housing Pigs are Raised in is a Primary Determinant of Their Welfare
The American Veterinary Medical Association (AVMA) has looked closely at all of the pig production systems and detailed the pluses and minuses of each. 
Overall AVMA did not find significant differences in the stress levels of sows in the different systems. Productivity or the ability for the animals to grow was also similar in the various systems. It goes back to the overall management of the system that makes the biggest difference in those factors. 
In any system, the care a farmer provides is key. A well-managed system of any kind is going to be superior to a poorly managed system of any kind.
Housing systems for pigs are designed to meet several objectives. First and foremost, farmers want their animals to be safe, healthy and comfortable. For pigs, this often means indoor housing to protect them from predators and disease and keep them warm in the winter and cool in the summer. In the case of sows, there are many options including outdoor systems, indoor group housing and individual housing sometimes referred to as crates. Each has their own advantages and drawbacks in terms of animal welfare.
The gestation period for a sow or time that they would live in an individual housing system is typically 114 days, or 3 months, 3 weeks, and 3 days. When sows are pregnant, they require a great deal of individualized care and adequate nutrition to support their developing litter.
The advantages of a gestation stall system are that animals are able to get better individualized diet, water and other care. The stalls also reduce aggression between the animals which can occur when they’re together in an open pen. This helps to prevent injuries to the animals. The disadvantages are the animals aren’t able to move as freely as they are in group housing, restricts their ability to perform foraging behaviors, and have less direct social interaction with other sows.