Amazingly, the superfit 5'10" Brazilian bombshell looked toned and ripped while sashaying down the runway in nothing but skimpy lingerie and high heels.
"When I first found out I was pregnant, I thought, 'Oh my gosh I don't think I'm going to be able to walk on the show,' and I didn't tell anybody so no one knew at the show that I was pregnant," Alessandra told Us.
"A week before, I told my booker, 'I don't think I'm going to be able to fit into the clothes because I gained a few pounds already,' but we were just quiet.
I cut all the sugars and sweets 10 days before and I got my trainer -- the one I usually get -- and we were doing lots of glutes and arms and back exercises."
While most pregnant women typically don't start showing until 3-4 months, few would be able to walk before a worldwide audience of millions in nothing but a bra and panties.
Ambrosio did a combination of ballet, squats, lunges and capoeira for 2 hours daily to regain her form after giving birth to daughter Anja in August 2008.
Alessandra, who's engaged to California businessman Jamie Mazur, isn't worried that pregnancy will hamper her successful modeling career.
"I'm thrilled," Ambrosio gushes. "I always wanted to have a big family so it was definitely my plan to have another baby. When I found out I was pregnant I was just as happy as I could be and I'm just enjoying every day.
"I love being pregnant! My body loves to be pregnant. I don't feel nauseous. I get a little more hungry but I just feel great."
