The 26-year-old Snooki & JWoww star, whose baby is due this fall, announced the news she's pregnant with a baby girl on her Celebuzz blog on Thursday.
Appearing in a video with her 20-month-old son Lorenzo, Polizzi said, "Jionni knows what we're having and he put some balloons in a bin for us, so we're going to find out what we're having right now and we're so excited!"
"You ready? Are you excited to have a sister or brother?" Polizzi asked her son, who said nothing but appeared to shake his head a little bit.
"No, you don't want it now? You want to be an only child? Well, you're not."
Polizzi then popped the lid off a bucket and tons of pink balloons flew out.
"Oh my goodness! We're having a girl! Yay!" the former Jersey Shore star said with a big smile. "Oh God, kill me. We're having a little girl, and I don't know how I feel about. I'm terrified, but we're really, really excited."
Polizzi and LaValle, also 26, plan to wed this fall. They broke the news of their engagement and the first pregnancy in March 2012.
Fellow Snooki & JWoww star Jenni "JWoww" Farley, who is Polizzi's best friend, is also pregnant right now with her first child. Farley, 27, revealed she was pregnant in December 2013 with fiance Roger Mathews. The couple has a baby girl on the way.