I don't consider birthmarks to be birth defects, no. And I don't believe the March of Dimes supports any type of birthmark funding at all.
Begin a Day of Awareness campaign in your local community. It's a chance to educate people, raise money, and help people affected by birthmarks everywhere.
If you email me at firstname.lastname@example.org
with your contact information, I'll send it on to the Day of Awareness coordinator.