ET's Cameron Mathison caught up with the actress at CinemaCon in Las Vegas on Wednesday, where she was out to promote her new movie, Unforgettable, on her first night away from her newborn son, Joshua.
"This is the first time that I have left him," Heigl revealed. "He's just a little over 3 months now and I'm just here for one day and I thought, 'You know, it's irresponsible of me to, like, disrupt his whole schedule for one day just because I have an issue.'"
"He's totally fine without me and I have a problem, so I'm trying to be the grown up here and make the right decision on his behalf," she added.
In fact, Heigl thinks the separation is harder on her than it is on her little bundle of joy.
"Oh, I'm sure [I'm having a tougher time than he is]," she said. "I already Facetimed him from the airport."
Baby Joshua isn't the only one Hiegl is missing -- she also got a little love from her girls before leaving.
"I should have moved things along because I was late and I needed to get going to make sure I got my flight this morning, but my middle [child], who used to be my baby, gave me this rare like snuggle session this morning," she gushed of 4-year-old Adelaide. "She's not much of a snuggler, like, she's more of a daddy's girl, and she'll come to me for a kiss or two, but never really snuggle snuggles. So I got that this morning too, so now I'm feeling especially sad and missing my babies."
"That's pathetic...this is ridiculous! It's one night!" the mother of three confessed. "Be more than mom for the evening! I'm in Vegas!"