Good Morning and welcome to Just answer. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
The gestation period in dogs is 65 days so often at 40 days, you will not see any changes besides possibly a weight gain. In some cases, you may not even see this. An ultrasound at this stage will tell you for sure if Rosie is pregnant.
Sincerely, Dr. Loretta