Cyrell wrote: "Maybe too soon to say but I'm thinking Eden. He's looking like his daddy."
The expectant mother also showed off a elephant teddy that played a recording of their son's heartbeat.
"How cute can hear the baby's heartbeat. Eden clearly enjoys playing with it," Cyrell added.
The heartwarming experience comes after the pair split in October, but got back together in early November.
In reference to Nicole Shiraz claiming Eden did not want his son, the former Love Island star said: "She has made it up and she is lying … It is a pretty low thing to do.
"I love children and I cannot wait to meet my son and be the best role model I can be. Cyrell will be an amazing mother."
Speaking exclusively to New Idea before they decided to reunite, Cyrell said: “I was desperate for our son to have a mother and a father – a happy home, a happy life.”
“Now I go into this all alone. It is devastating. It is the last thing I ever wanted. Everyone thinks this was an easy decision. It really wasn’t.”