At 4 weeks of pregnancy, a cat's physical changes may not be very noticeable externally. The cat's abdomen may not appear significantly larger, but there could be subtle signs of pregnancy. The cat's nipples may become more prominent and slightly enlarged, and their color may darken. However, these changes can vary among individual cats, and some may show more obvious signs of pregnancy at this stage. To accurately determine the stage of pregnancy, it is recommended to consult a veterinarian. A veterinarian can perform a physical examination, palpation, or ultrasound to assess the pregnancy accurately and provide guidance and care tailored to the specific needs of the pregnant cat. Regular veterinary check-ups throughout the pregnancy are essential to monitor the cat's health and the development of her kittens.