Most female dogs won't let you know they're pregnant until they're halfway through gestation. There may be subtle changes in behavior, but only the very observant will notice them until around the fourth week of a dog's 61- to 64-day pregnancy.
She Might Be Sleepy
Early in your dog's pregnancy, she may become more clingy and affectionate. Some dogs, though, become more aloof. She may sleep more. Her nipples can appear pink and slightly larger, although this may not be noticeable until she's several weeks along.
Lack of Appetite
By her fourth week of pregnancy, she might lose her appetite and start refusing food. Some dogs just eat a bit more slowly; others won't eat at all. This symptom generally lasts for about a week, although some dogs lose their appetite until the litter is born.
Not every dog goes off her food. Some continue eating normally throughout their pregnancy and become hungrier. Increase the amount of your dog's food in the second half of her pregnancy to help her prepare for the task of feeding her puppies.
If she is picky about eating, add another meal to her day rather than increasing the amount of her normal feedings.
A mother dog will begin to gain weight around her fifth week, but many don't appear pregnant until the sixth or seventh week. Depending on the size of the litter she is carrying, her abdomen will become rounder between the fifth and sixth weeks. Her gait will change. She'll slow down and be reluctant to exercise. She will want to urinate more frequently.
Provide gentle exercise during the second half of pregnancy but discourage jumping.
By her seventh week, she will be noticeably pregnant and nesting behavior will begin. She will dig at bedding and seek out quiet places. This behavior will increase as delivery approaches. Prepare a whelping box or a quiet area for her to deliver the puppies at least a week before her due date, and encourage her to spend time there. Otherwise, she will find her own delivery area -- a closet or bed you'd rather she didn't use.
Most mother dogs experience a drop in body temperature about 24 hours before whelping, usually two degrees or more. She might refuse food from 12 to 24 hours before whelping. You may notice some milk leaking from her nipples, along with increased nesting behavior. When this occurs, puppies will soon follow.