The 36-year-old actress, writer and director said during Thursday's episode of The Late Late Show with James Corden that thinking of Hargitay, who plays Det. Olivia Benson on Law & Order: SVU, helped keep her calm during her pregnancy.
"I try to be a generally healthy person," Gerwig said. "I try to meditate, and when you're pregnant they do these guided meditations for pregnant women to make them feel good about that."
"I was doing these guided meditations and they always say like, 'Imagine something really comforting.' I think you're supposed to imagine a beach but I would always imagine Mariska Hargitay's face," she added. "I find her so comforting."
Gerwig said Hargitay is "very much a part" of Harold's life without knowing it.
"I think that's why my baby is so happy," the director said. "She's very strong and compassionate and non-judgmental, and I feel like my baby felt her love."
"Harold woke up, and Greta brought Harold to bed. We were just sort of hanging out and not looking at anything, but aware that maybe there was news," Baumbach recalled.
"Then I thought, no matter what happens, it's this baby. A baby's laugh!" he said.
Gerwig and Baumbach discussed their respect for each other and professional rivalry in the Dec. 13 issue of The Hollywood Reporter. The couple started dating in 2011 and have co-written the films Frances Ha and Mistress America.