When Do Pregnant Dogs Start To Show. After the first month, the dog's appetite may increase and she will gain more weight. You won't see physical change for the first half of gestation.

Usually, she would lick her vulva excessively a day or shorter before her due date. Ordinarily the dog's abdominal area will be flat with small nipples. Most dogs don't gain significant weight or start to show the pregnancy until the sixth week.