The 27-year-old actress and her husband Brian Austin Green - who already have a 10-month-old son, Noah - are expecting their second child together and are "very happy" with the news.
Leslie Sloane Zelnick, a representative for Megan told the New York Post newspaper: "I can confirm Megan is expecting her second child with her husband Brian, they are both very happy."
The brunette beauty is currently filming 'Teenage Mutant Ninja Turtles' and although she's in the early stages of her pregnancy, she remained tight-lipped about the news so that it didn't interfere with her work.
The couple - who first started dating in 2004 and tied the knot in June 2010 - were very secretive when they were expecting Noah and they managed to keep the birth of their son under wraps for two weeks before Megan eventually took to her Facebook page to confirm the rumours.
She wrote: "We are humbled to have the opportunity to call ourselves the parents of this beautiful soul and I am forever grateful to God for allowing me to know this kind of boundless, immaculate love.
"Thanks to those of you who wish to send your positive energy and well wishes."
Megan - who is also stepmother to Brian's 11-year-old son Kassius, his child with ex-partner Vanessa Marcil Giovinazzo - recently expressed her desire to give Noah a sibling to play with.
She said: "All I wanted to do my whole, whole life was have a baby and, now, I've finally done it.
"I just want to give Noah as much of myself as I can. And I want to have more kids. That is where my heart is."