Producers are interested in utilising farrowing systems with reduced confinement to improve sow welfare. However, concerns of increased mortality may limit commercial uptake. Temporary confinement systems utilise a standard crate which is opened 3 to 7 days postpartum, providing protection for neonatal piglets at their most vulnerable age and later increased freedom of movement for sows. However, there is anecdotal evidence that piglet mortality increases immediately after the temporary crate is opened. The current study aims were to determine if piglet mortality increases post-opening, to trial different opening techniques to reduce post-opening piglet mortality and to identify how the different opening techniques influence sow behaviour. Three opening treatments were implemented across 416 sows: two involved opening crates individually within each farrowing house when each litter reached 7 days of age, in either the morning or afternoon (AM or PM), with a control of the standard method used on the farm to open all crates in each farrowing house simultaneously once the average litter age reached 7 days (ALL). Behavioural observations were performed on five sows from each treatment during the 6 h after crate opening, and during the same 6 h period on the previous and subsequent days. Across all treatments, piglet mortality was significantly higher in the post-opening than pre-opening period (P<0.0005). Between opening treatments, there were significant differences in piglet mortality during the 2 days after crate opening (P<0.05), whilst piglet mortality also tended to differ from crate opening until weaning (P=0.052), being highest in ALL and lowest in PM. Only sows in the PM treatment showed no increase in standing behaviour but did show an increased number of potentially dangerous posture changes after crate opening (P=0.01), which may be partly attributed to the temporal difference in observation periods. Sow behaviour only differed between AM and ALL on the day before crate opening, suggesting the AM treatment disrupted behaviour pre-opening. Sows in AM and PM treatments showed more sitting behaviour than ALL, and therefore may have been more alert. In conclusion, increases in piglet mortality after crate opening can be reduced by opening crates individually, more so in the afternoon. Sow habituation to disturbance before crate opening may have reduced post-opening piglet mortality, perhaps by reducing the difference in pre- and post-opening sow behaviour patterns.