The expectant mom spoke with ET's Kevin Frazier at a special screening of her new comedy, Bad Moms, in Los Angeles on Thursday, where Kunis explained, "I forgot how far along I was today. I think with the first one, you're so enamored with the initial experience that I was constantly checking the app, 'What fruit size is the baby? Is it the size of a grape or an avocado?'"
"Now I'm like, 'Wait, how far along am I?'" she added. "You're busy running after the other one and working full time."
Kunis and Kutcher, who welcomed their first daughter, Wyatt Isabelle, back in October 2014, recently revealed that they were getting ready to welcome another baby.
In Bad Moms, Kunis plays Amy, a hard working mother of two teenage kids who gets fed up trying to be perfect and decides to take a walk on the wild side.
"Sometimes babies projectile poop, and it was one of those days where there was a lot of poop," Kunis recounted. "I turn around and he's like, 'I got it babe!' and I was like, 'Great!' And then I turned back around, and he literally bathed her in the sink, which is fine, and then wrapped her in an entire roll of paper [towels]."
I was like, 'What are you doing?' and he's like, 'Drying her up!' and he goes, 'I couldn't find the towel.' And I literally was like, 'What is happening!?'" she continued. "She was cocooned in this little Bounty roll, and I was like, 'Oh my god I love you so much!' It made me so happy. I took so many photos of it. I literally was dying laughing."
Kunis' Bad Moms co-star Christina Applegate also opened up about one of her own hilarious parenting fails, telling ET about the times she and her husband, Martyn LeNoble, accidentally let their daughter listen to some age-inappropriate content.
"When we go to pick her up, we listen to Howard Stern in the car," Applegate shared. "And there have been times where we have forgotten to turn it off when she got in the car, and it's right at a really inappropriate moment."
"That's happened to both of us. I think it's happened to him more than it's happened to me because I try to remember [to change the channel]," she added.
Kunis spoke with ET on the set of Bad Moms in February where she gushed about wanting to expand her family prior to announcing her second pregnancy. Check out the video below to hear more.
Bad Moms opens in theaters July 29.