Relationship between spontaneous behaviour at late pregnancy and reproductivity in mice

The spontaneous behaviour at late pregnancy was measured as motor activity by Supermex in SHN mice, which have a rather high still-birth rate. The activities during both light and dark phases as well as during the total period were significantly higher in mice with still-birth than those with normal delivery. Meanwhile, in normal delivery group, there was little correlation between the spontaneous activity and the reproductive parameters, except for litter size or total pup weight. These results strongly suggest that calmness, especially at late pregnancy is prerequisite for normal delivery and that reproduction itself after delivery was not markedly affected by the behaviour of mother at late pregnancy.