The X Factor judge surprised fans this week by announcing she had secretly married her French partner of three months, Jean-Bernard Fernandez-Versini.
Sending her congratulations via Twitter, Coyle wrote: "Aww @CherylOfficial you must be having an amazing time. I am so happy for you! Good luck with everything. Come join the baby club. Best ever."
Cole responded by sending kisses to Coyle, who has relocated to LA.
The Northern Ireland star became the first member of Girls Aloud to have a baby when she gave birth in February to her daughter, Anaíya, with American football player Jason Bell.
Fellow band member Kimberley Walsh is currently expecting her first child, who is due in October.