Jennifer Lawrence was five months pregnant while filming movie about woman experiencing postpartum psychosis

Lawrence, who revealed she was five months pregnant with her second child while filming the movie, which also stars Robert Pattinson, said becoming a mom changed her in ways she never imagined. 

Discussing the hardest day on set, Lawrence said it included one of many sex scenes. 

"The day before our first day, Lynne showed Rob and I a scene from 'If' and these characters are attacking each other like tigers. And she said, 'You'll do it naked, yeah?' And we're like 'Oh, OK,'" Lawrence said. "And that was the first day on set."

Pattinson, who also became a parent last year, admitted that "trying to figure out what your role in the relationship is afterwards is incredibly difficult."

"Like he's just a guy. He doesn't seem to be the guy who is looking at TikTok reels of parenting and stuff," he said of his character. "He's just kind of hoping the relationship will go back to what it was and not understanding why this is happening to them, why this intruder has entered this relationship. I guess it's a fear that everyone has as soon as they have a kid."