The crushing of piglets by the sow has always been a problem, but it has become increasingly prevalent in farrowing systems that loose house the sows. This article, reviewed papers pertaining to piglets crushing related to sows’ lying down and rolling behaviours. Very little research has been conducted on the rolling behaviours in sows. It is known that sows will roll more frequently when they are housed on concrete versus plasticized floors. Also the more quickly a sow rolls over, the higher the risk of piglets being crushed. Considerably more work has been done on the lying behaviour of sows; for example, the sequence of movements made during the process of lying down has been clearly broken down into five stages. Once again the speed of the movements, especially when the sow lowers her hindquarters, could possibly be related to piglet crushing. However, if a sow leans against a surface or if performs pre-lying behaviours (moves around, paws, roots, and gathers the piglets to in an area opposite of where she will lie) the risk of piglet crushing is reduced. As well, how responsive the sow is to a piglet that has become trapped underneath her affect the incidence of crushing, which may be influenced by the piglets’ responses to crushing (vocalizations), how long after parturition the incident occurs, the amount of space provided to the sow and bedding. Various factors such as domestication, breed, muscle control, previous and current housing may impact the methodology and how quickly a sow lies down. Piglets’ responses to crushing and space allocated to the sow may impact the exhibition of pre-lying behaviours. The authors believe all these factors should be taken into consideration when designing and managing the farrowing environment of the sow to help reduce the incidence of piglet crushing. However, the authors also call for more research in this area, as they believe a better understanding of these behaviours is needed.