Yes — if you avoid excessive weight gain, you can lower the possibility of stretch marks appearing on your skin. Moderate exercise during pregnancy may help you achieve that goal, as maintaining physical activity is the key for a healthy weight gain. This way, you'll be able to decrease the amount of unnecessary fat tissue and reduce the stretching forces that apply to your skin.
However, you shouldn't forget to take proper care of your skin: hydrate and oil it as often as it needs.  A protective routine should start even before the pregnancy itself. If your skin is in good condition, it has better chances to successfully endure all the greatest challenges during the second and third trimester of the pregnancy.
PS: Don't forget to drink plenty of water! Read more