A PHOTO of two friends comparing baby bellies has proved that when it comes to pregnancy, every body is different.

The discussion started after Australian fitness model Chontel Duncan, who was 21 weeks pregnant, posed belly-to-belly for a photo with her friend Nat, who was four weeks further along in her pregnancy.

Highlighting differences in each woman's shape and size, the image prompted Duncan to share a few home truths about pregnancy.

"Each woman carries different, and this most certainly doesn't mean one is doing something wrong or not healthy" she wrote. "We both have healthy growing babies, and we both have had incredible pregnancies so far, feeling amazing and full of energy."

Duncan, who is experiencing pregnancy for the first time, said she was grateful for advice from her friend, who was expecting her third child.

The fitness enthusiast later shared an update, posting a pic to Instagram of her pregnancy figure a month away from her due date.

-nzherald.co.nz