First comes love, then comes marriage, then comes baby in the baby carriage. But when it’s three babies, you’re gonna need a larger home.

John Legend, 41, and Chrissy Teigen, 34, who are expecting their third child — a boy — have just bought a nearly 11,000-square-foot home in Beverly Hills for $17.5 million, the property’s listing brokerage told The Post.

The Wall Street Journal first reported the deal, adding that this purchase comes shortly after the couple listed their smaller, roughly 8,500-square-foot home, also in Beverly Hills, for a larger asking price of $23.95 million. Teigen’s mother, Vilailuck Teigen, a k a “Pepper Thai,” also lives with them.

JB Builders recently completed this new 10,700-square-foot spread, which has six bedrooms and nine bathrooms. The home includes marble and wood details, the listing notes, as well as 24-foot ceilings and floor-to-ceiling windows.

Also floor-to-ceiling, a double-sided fireplace that has a formal dining room on one side and a family room on the other. Teigen, also a cookbook author, will have Miele appliances, an oversize eat-in island and a polished marble wall in the kitchen.

Entertaining areas include a bar and lounge, and a 500-square-foot media room with an automatic 145-inch projection screen.

As for the private quarters, a 30-foot interior bridge leads to the master suite, which has suede panel walls, two walk-in closets and pocket doors that lead to a balcony with recessed infrared heaters.

Outside, there’s a 6,600-square-foot landscaped motor court, a barbecue area and a 100-foot saltwater infinity pool.

Although an exciting new home for the family, Teigen has struggled with a difficult pregnancy, having recently been placed on bed rest.

Sally Forster Jones of Compass represented the developer in the deal; Marshall Peck of Douglas Elliman represented Legend and Teigen.