My cats were quite clingy during the later part of my last pregnancy and are doing the same this one. I can't recall any exact behaviour prior to labour last time, I will try to take notice this time. I can be hard to tell though, as they do get clingier as it gets colder and if they want something. I am getting worse at feeding them on time these days. Actually they do seem to want to get closer when I get those feelings that something could be starting.