The 45-year-old star is expecting a baby with husband Will Swenson, 42.
“Who knew that tap dancing during perimenopause could lead to pregnancy?” McDonald tweeted out. “Will and I are completely surprised — and elated — to be expecting a new addition to our family.”
McDonald has a 15-year-old daughter from a previous marriage, and her husband has a 13-year-old and 10-year-old son. The two were married in 2012.
McDonald is currently starring in the 1920s-themed hit Broadway show Shuffle Along and will take three months maternity leave starting in July.
The six-time Tony Award winner recently graced the cover of Essence Magazine in April.
“I am so very grateful to everyone in New York and London for allowing me to rearrange my schedule to accommodate this little miracle,” McDonald said in a statement.
“While I’m disappointed I have to postpone my West End debut in Lady Day, I’m glad I’ll be able to spend a little more time in Shuffle Along this summer and will look forward to setting up a 1920s-themed nursery in my dressing room when I return to the show.”