The two divas "bumped into" each other on the air Friday when they were scheduled to do back-to-back interviews with Ryan Seacrest on his KIIS-FM radio show.
With Aguilera about to sign off, Seacrest asked her to say hello to Pink on the other line, who noted Aguilera – mom to a 2-year-old boy, Max – could probably offer her some "mommy advice."
"Congratulations! I just heard the amazing news," Aguilera replied. "I'm so happy for you. Join the club."
"I feel like I really am joining a club," Pink said.
Aguilera, 29, then proceeded to interview her fellow singer – whose doctors believe is expecting a girl – about her pregnancy. "How are you feeling? Do you have morning sickness? How's it feeling for you?"
"No, unfortunately," Pink said as Seacrest stayed mum in the background. "I feel like if I had morning sickness I would have lost some weight. But I've kept everything down."
"It's good," Aguilera insisted. "You're eating for two now – use it while you can, right?"
Aguilera later suggested that they get their kids together down the line, saying "We have to have play dates." Pink chuckled at the suggestion, and Aguilera picked up on her hesitation – but Pink, 31, explained it wasn't personal.
"The reason I laughed is I was with these two girls last night who used to be best friends until their kids started fighting," Pink said. "It's pretty funny what that does to people."
Aguilera agreed friends can cross boundaries, saying, "Don't discipline my kid, thanks."
Added Pink, "What if your kid punches my kid? Then what happens?"
"Yeah, really messed up. And the moms start battling it out!" Aguilera said.
Not Jillian's FaultWhen Seacrest took over, Pink absolved Jillian Barberie Reynolds, who leaked news of her pregnancy on Twitter, telling Seacrest that actually, "It was my drummer's big mouth … [He] beat her to it."
Seacrest also asked her to elaborate on why she's "terrified" of having a girl.
"I feel like I 'get' boys," Pink explained. "I've always been a boy's girl. Boys are easy, they just break stuff."
As for the father of her unborn child, motocross racer Carey Hart, Pink says it was a given she'd have kids with him. "Two weeks after I met him I knew it," she said, and so did he.
"We were at Macaroni Grill – we were going super romantic – and he was like so, you wanna have kids? And I was like no, I'm 22," she says.
But after nine years together, now they're both ready.