Chrissy Teigan and John Legend
Model Chrissy Teigen and singer John Legend are already parents to 16-month-old daughter Luna. VALERIE MACON/AFP/Getty Images

Chrissy Teigen and husband John Legend are expecting their second child, the model announced on Tuesday (21 November) via Instagram.

In an adorable Instagram video, 31-year-old Teigen asks her daughter, "Luna, what's in here?" as she points towards her belly.

"Baby!" the 16-month-old little girl replies. The model and cook book author shared the video on social media, captioning the announcement video, "It's John's!"

Legend, joking replied to his wife's post with: "Maury will have the final word on this".

The Grammy-winning singer spoke to PEOPLE Friday (17 November) and revealed that the couple were "working on" baby number two and that "hopefully it will be soon".

When asked how little Luna Simone will be as a big sister, 38-year-old Legend responded: "I have no idea. She is very sweet and she likes to share, so hopefully that will translate."

The soon-to-be mother-of-two recently opened up about adding another little one to her family. "We're still trying... I'm going for, I mean hopefully in the next few years, because for me I really want to just knock 'em out," she told E! News.

"That's my dream, I want to just be pregnant kind of for the rest of my life," she added. "Not for the rest of my life, but the rest of my fertile life. So we'll see."

The couple has also opened up about their difficulties conceiving and their experience with IVF treatment, Us Weekly reported.

"Having a baby is a big challenge for a couple, and going through that together strengthens your bond because if you make it through [having a child], you know you can make it through anything," Legend said to Cosmopolitan magazine in August.

"We're lucky that we're living in an age where we can conceive in other ways," he continued. "[IVF treatment] brought us Luna and hopefully it will bring us a few more awesome kids, too."

The couple got married in September 2013 in Lake Como, Italy.