"As soon as we got married we wanted to start [trying] and we were very blessed and God willing, we were able to make it happen soon after the wedding!" Firestone toldUs Weekly in a Tuesday report.
The 33-year-old Firestone Tire company heir and 30-year-old model/actress initially met in 2005. After getting engaged in 2007, the couple were married on June 6 at St. Mark's in the Valley Episcopal Church in Los Olivos, CA.
Following their wedding, the couple honeymooned in Cabo San Lucas, Mexico, which is where Firestone thinks the baby may have been conceived.
"We're just over the moon, we're so happy," Firestone told Us. "It's possible it's even a honeymoon baby!"
"I was in a state of shock about a month ago when we found out," Firestone told Us. "[Ivana] had a feeling in the middle of the night so she got up and she took the pregnancy test and then came and jumped on the bed, screaming and yelling. We ended up staying up the rest of the night, laughing and talking about it."
The couple has decided not to find out the sex of the baby, which is due in mid-April 2009.
"There's very few surprises left and I already wasted a big one on Ivana when I proposed to her," he told Us. "This will be our big life surprise."