A.J. Cook by Monty Brinton/CBS A.J. Cook by Monty Brinton/CBS
Criminal Minds ' Jennifer "J.J." Jareau's life will soon hit a bump - a baby bump.

A.J. Cook returned from the writers' strike with more than just an eagerness to get back to work. She and husband Nathan Anderson found out she was pregnant with their first child while she was shooting the movie

Misconceptions, in which she plays a surrogate mother. "She's very Method," cracks Minds exec producer Ed Bernero. Bernero and his staff immediately began rewriting scripts to plant a romantic backstory for J.J. "The way this show works, we couldn't really hide it," says Bernero. "All seven of them walk into rooms together all the time, so it really was a no-brainer: 'Well, we better get her a boyfriend.'" So in the April 30 episode, the BAU team once again crosses paths with Det. William LaMontagne Jr. ( Dirt's Josh Stewart), who flirted with J.J. during a jaunt to New Orleans in February 2007. "There was a connection between the two of them right away," Cook says. "Apparently, we've been getting it on for a year." Four months along, Cook has already begun blocking her growing midsection on camera. "It's in full force - it just popped," says the 29-year-old Canadian actress. "I don't want it to look like J.J.'s been hitting up the doughnut store." Since the fourth season starts shooting less than a month after the current one ends, Cook's belly will swell on screen. "It's going to be interesting," Cook says. "I'm kind of freaked out, because not everyone has to go through their pregnancy on national TV." - Jay A. Fernandez