Now at age 46, the "Beauty and the Beast" star has a second baby and a first with her husband and fellow Broadway star Will Swenson.
The couple welcomed daughter Sally James last October.
McDonald said she has changed as a mother since the first time around.
"I’m calmer this time around, 16 years later," she told People magazine. "Or maybe it’s that I’m just tired because I’m older, but I don’t sweat the small stuff as much."
And although Sally James is only 5 months old, she already has a larger-than-life personality, her mother said.
"In some ways, I don’t worry about her — this is a very strong personality, I’m seeing it already!" she said. "This is someone who’s not gonna let anybody walk over her at all. In fact, she’ll be the one doing the walking."
"Who knew that tap dancing during perimenopause could lead 2 pregnancy? @thewillswenson & I are completely surprised but elated 2 b expecting," she wrote on Twitter last May.
McDonald, who formerly starred on the ABC series "Private Practice," also has a daughter, Zoe, from a previous marriage, and Swenson has two sons with his former wife.
"Zoe is such a fantastic big sister to Sally James," McDonald said of her older daughter. "That’s just who she wants to hang out with. Every time Zoe walks into the room, Sally lights up. And that’s so important to me."
McDonald and Swenson, 43, married in 2012 at their home in Croton-on-Hudson, New York.