She found out via the media like everyone else.
"I had no idea Heidi was pregnant," Stephanie told OK! magazine. "Spencer and Heidi tend to do things in their own way. I'm really happy for them both."
Stephanie, who was often featured on "The Hills" with the reality TV villainous couple, thinks Heidi will basically be super-mom.
"Heidi has wanted a kid for 10 years, she's born to be a mom," Stephanie, who now lives in London, said.
Spencer and Heidi revealed their pregnancy on the cover of Us Weekly in April.
When Heidi told Spencer, he recalled, she was stunned. "The look on her face, I can't even describe it," he told Us. "She was literally glowing. I thought she was about to say she made muffins or banana bread."
After she told him, Heidi cried and Spencer hugged her.
"I was like, 'Whoa, that's way more exciting than banana bread!' … Heidi has wanted to be a mom since the day I met her," Spencer said.
Heidi added, "I wanted a baby three years ago. Spencer was a little hesitant. Then one thing after another came up. We had work obligations, like 'Celebrity Big Brother' in the U.K., which I did not want to be pregnant for. I'm actually really thankful we waited. I thought I was ready in my twenties, but with everything we had going on, it just wouldn't have been a good situation for us."
Spencer said, "It might never be the perfect time, so we said, 'Let's move forward.'"
On April 25, Heidi and Spencer celebrated their 8th anniversary. She took to social media to praise the father of her unborn child.
"Happy 8 year anniversary @spencerpratt ! Thank you for the best gift… a baby," she wrote on Instagram. "So excited to continue on this blessed journey together! Love you ❤️."