"When Michael and I want to share big news, I insist on creating a Beyoncé-inspired video montage," said Pitt, sharing a video of memorable moments with her young family.
"Baby #2, we can't wait to meet you PS I promise we'll find you a more appropriate name soon ."
Pitt hinted she was itching for another baby in October during an interview with Stellar Mag.
"I feel like if you have one child, you're really lucky — if you have two, you're even luckier," she told the publication, according to news.com.au.
She also told the mag parenthood has impacted on her relationship with her fiance, who has been by her side for the past 10 years and vowed he would marry her if she survived her traumatic injuries.
"(Parenthood) changes every day," Pitt said.
"Some days are joyful, some are extraordinary, some you're really irritated and really short with your partner and you're tired. Mum is just around the corner and Michael is a really hands-on dad, but still I find it hard. Motherhood is definitely not an easy job."
Following her horrific incident while running an ultra-marathon in 2011, Pitt became the poster girl for resilience.
She runs School of Champions, her online mindset coaching program, and this year released her new ebook, Good Selfie.