Starvation and crushing by the sow are the two main causes of piglet mortality prior to weaning, thus it is obvious that the behaviour of the sow influences piglet survival. In order to increase the understanding of the behavioural mechanisms influencing piglet performance, we recorded undisturbed general activity (standing or walking), frequency of standing-to-lying posture changes (standing-to-lying) and carefulness at standing-to-lying during a 5-week lactation for 24 Yorkshire sows. Carefulness was estimated using four components of sow anti-crushing behaviour (rooting or sniffing piglet prior to standing-to-lying, careful standing-to-lying and no piglets in danger zone at standing-to-lying).We investigated the changes in and consistency of these behaviours throughout lactation, as well as the associations between different aspects of behaviour. Secondly, we examined whether sow activity level and frequency of standing-to-lying were related to nursing behaviour, sow body resource mobilisation (measured as blood concentration of non-esterified fatty-acids (NEFA)) and piglet growth. In addition, we grouped the sows according to litter mortality and according to whether they had crushed any piglets or not and determined if these groups differed in the above mentioned behaviour patterns.Both the activity level and frequency of standing-to-lying of sows increased and had high within-sow repeatability throughout the 5-week period. Carefulness at standing-to-lying did not change significantly over lactation. The variable showed very low within-sow repeatability and only one aspect of carefulness (rooting of the floor) decreased in the later stages of lactation. No significant associations were found between activity level and frequency of standing-to-lying on the one hand, and nursing behaviour or growth of the piglets on the other, except for a positive correlation between frequency of standing-to-lying and observations of the sow lying on her udder. Sows with low mortality (less than two dead piglets) in their litters were more active on day 3 postpartum (pp) than sows with high mortality. The difference was especially clear when comparing sows with or without any crushed piglets in their litters. Sows with no crushed piglets also showed a higher incidence of rooting the floor on day 3 than sows with at least one crushed piglet.Activity level of the sow seems to be an individual characteristic that has possibly been decreased by selection for large and docile animals, suited to intensive production systems. Activity level and amount of rooting performed at standing-to-lying appear to be important aspects of good maternal characteristics. Our results encourage studies of selection for enhanced piglet survival via improved maternal abilities.