During the final three weeks of pregnancy the mother should be separated from other cats in the household as well as cats from outside the family. (2ndchance.info)
Make sure you have enough litter boxes for the number of cats in the household and that they are easily accessible. (catbehaviorassociates.com)
If multiple cats in the household are suffering from similar problems, then a contagious disease will be considered. (cat-health-guide.org)