The actress, 40, who is due in October, “just hasn’t ever wanted anyone beyond her close friends and family knowing more than they had to,” an insider tells PEOPLE in this week’s issue. “And Ryan is certainly private and always has been.”
Now living together in 33-year-old Gosling’s modest Studio City home, the couple also embraced a lifestyle that aided their efforts for secrecy.
“Their lives completely changed as soon as Eva got pregnant,” says a source. “They used to travel all over the place together and go on hikes with their dogs.”
But in the last few months, Mendes “barely left the house,” adds the source. “Ryan has been taking care of her, picking up food and running errands. He has been very supportive about keeping things a secret.”
The actress, who was last photographed in March, is also proving to be adept at covering up her baby bump as she demonstrated in an L.A. parking garage on July 9. She was also conspicuously absent at this year’s Cannes Film Festival, where the couple’s film, Lost River, premiered in May.
What can’t be contained is the pair’s excitement.
“This has been a long time coming,” says a pal. “Ryan and Eva definitely discussed children before. She knows how much he wants to be a dad and he’s going to be an amazing father.”
For more on Gosling and Mendes’ relationship and her pregnancy, pick up this week’s issue of PEOPLE, on newsstands Friday
• With reporting by JENNIFER GARCIA and AILI NAHAS