Chyler Leigh and Nathan West with children Anniston, Noah and Taelyn
08/24/2009 AT 06:25 PM EDT
Chyler Leigh's family has been in the midst of a steady growth spurt for the past six years. But with the May 7 birth of their third child
, Anniston Kae, the Grey's Anatomy
star and her husband, actor Nathan West, have found that parenting gets a little bit easier with each addition to their clan.
"Going from zero to one is a huge shock," Leigh, 27, tells PEOPLE. "One to two was a little more challenging. Two to three was a bit more challenging, but once you get used to multiples you figure out how to put things together quicker. You learn how to organize. With number three coming, you get more confident as a mom. It's like calm mom, calm baby."
It doesn't hurt that Anniston, whose older siblings are Noah, 5 ½ and Taelyn, 2 ½, is a mellow baby. "She started sleeping through the night at two months," Leigh says of the infant, who was born just 10 days after Grey's
's fifth season wrapped.
Anni, who is going to set with her mom and a caregiver most days is "so easy going. She's so happy to be held, but good at having her own independent time. That's made a big difference," she says. "I think she kinda knew she was coming into a hectic household!"
The well-behaved baby has already won over the actors on her mom's hit show. "Justin [Chambers] nicknamed her Baby Elvis because of her mohawk," Leigh says.
Leigh and her husband don't plan on making another addition to their family any time soon. "Three kids is a lot," says West. "But I couldn't imagine our family without her. She just completed it."
For more from the interview, as well as an additional photo, PEOPLE's Celebrity Baby Blog