How do labradors react when they are going to deliver their puppies?

Dogs, like women, can vary a lot in their behavior just before delivery. In general, labs and most dogs will stop eating about 12-24 hours before delivery. However, I have seen a few dogs who actually suddenly started eating almost immediately before giving birth.

They also tend to act restless, pacing, walking around, building a nest -- or trying to move their nest to another spot if they decide they aren't happy with the location. Also, if you are taking their temperature twice daily, at approximately the same times each day, you will find her temperature drops about a degree or a little more than that, and she usually gives birth within 12 hours of the initial temperature drop. Sometimes it is hard to see the drop; it can be very slight or it can drop and go back up to normal, or if you take her temperature at the "wrong" time of day, it could drop in between your checks, and so instead of the pups coming within twelve hours, they may come an hour later.

the normal gestation is 63 days, and dogs are generally pretty close in timing, however, the pups could be born a week or so before or after the 63rd day -- it is not possible usually to know exactly the day of conception, so you are just "guesstimating" on the 63 days. you want to make sure she has a comfortable, safe place to have her pups, a few weeks before birth at least, and make sure it is out of the way -- too much traffic and other animals will cause mom to be very nervous and could even cause her to hurt her pups (usually accidentally== jumping up at every noise and then accidentally lying down on one of the pups).