The Grey's Anatomy actress, 39, details her tight-knit relationship with her three daughters for PEOPLE's cover story this week, including what she's learned since becoming mom to Eliza, 8, Pippa, who turns 4 next month, and Lucky, 10 months.
Scorsone reflects on raising Pippa, who was born with Down syndrome, saying her "difference lit a match in my life and in the life of my family."
"When my daughter Pippa was born, I was scared. I didn't know anything about trisomy 21, the name for the occurrence of a third copy of the 21st chromosome, better known as Down syndrome," she says. "... I didn't know anything. All I knew about Down syndrome was that people were afraid of it, so I figured I should be too."