Alessandra Ambrosio presents new Philips 'Satin Perfect' at ME Hotel on March 5, 2012 in Madrid, Spain. Credit: Juan Naharro Gimenez/

Oh, boy!

Pregnant-again supermodel Alessandra Ambrosio will welcome a son when she gives birth later this spring, she announced on Facebook Tuesday.

The Victoria's Secret catwalker, 30, wrote "It's a Boy!" in the sand while posing on the beach (covering up her bump in a t-shirt and shorts) in a sweet photo on Facebook.

"We really tried to keep it a surprise but we were too anxious!" she explained to fans beneath the pic. "Soon, we will have a little boy to rock our world!!"

The little guy will join big sister Anja, Ambrosio's 3-year-old with fiance Jamie Mazur.

"Family is the most important thing for me and I'm thrilled to be adding to the family," the Brazilian stunner told Us Weekly in late December when she announced her pregnancy. "I'm fortunate to have a loving and supportive family. It's a blessing that it will soon be growing."