The 25-year-old brunette beauty and her hubby of nearly two years, Brian Austin Green, are expecting their first child together and couldn't be more excited, Star magazine is exclusively reporting.
"They just found out and are incredibly excited," a source close to the couple told Star, noting that the pregnancy was unexpected.
However, it's unlikely the Transformers actress will be going public with the news just yet, as the source says: "It's still early, so they are only telling close friends and family members."
Since tying the knot in 2010, Megan has become stepmother to Brian's 10-year-old son, Kassius, who he had with ex Vanessa Marcil.
"Megan has become a great stepmom, and Brian knows she'll be wonderful with the baby," the source said.
"She has really grown in the past couple of years. Megan used to only be concerned with her career, but now family comes first."
To get all the details on Megan's pregnancy, check out the new issue of Star magazine -- on newsstands Thursday.