Naomi Watts and Liev Schreiber welcomed their first child, a healthy baby boy, on Thursday, PEOPLE has confirmed. Alexander Pete Schreiber, who was born at 3:59 p.m. in Los Angeles, weighs 8 lbs., 4 oz, and is 22.5 inches long, according to a rep for Watts. Just last weekend, Watts, 38, and Schreiber, 39, celebrated with a baby shower at their Los Angeles-area home. Among the approximately 15 guests were Kate Hudson and actress Carla Gugino. The pair started dating in 2005, and news of the baby was first announced this past February by Schreiber himself on NBC's Late Night with Conan O'Brien. When it came to selecting a name for the child, Schreiber told O'Brien, "I'm trying to stay out of it all," though he made clear the baby would not be called Liev. "It's an awful name," said Schreiber. "It's probably the most oft-mispronounced name in showbiz." Last month, Watts told PEOPLE of her pregnancy: "[I'm] just being relaxed and moving at a much slower pace and enjoying it. I'm just really happy to be pregnant." The delivery was first reported by Life & Style magazine.