As revealed yesterday, Kirsty will give birth at the Rovers Return next month after her waters break following a furious argument with Tina.
Although mother and baby are both fine, Tina's treatment of Kirsty (Natalie Gumede) does not go down well among the local residents.
Keegan told Soaplife: "Tina just loses it. [The argument] escalates into a bit of a scuffle, and Kirsty falls back into one of the tables.
"Tina feels incredibly guilty. Marcus has to deliver Kirsty's baby in the pub. It's not what Tina would have wished on anyone. Tommy really wants to be loyal to Tina, but even he tells her it was a stupid thing to do. It happens in a busy pub with everyone watching, and Tina and Tommy become public enemy number one."
Confirming that the latest problems will put a strain on Tina and Tommy's relationship, the actress continued: "They're desperately trying to keep a united front, but the cracks are starting to show. It seems something goes wrong for them every day, and they simply don't have the chance to be a normal couple."
Earlier this week, reports revealed that Tina will offer to become a surrogate mother for Izzy Armstrong and Gary Windass in a bid to solve her own financial problems.
Teasing the story for the first time, Keegan commented: "Tina saw her father Joe suffer badly because of his financial woes. She's in a desperate situation, and you really don't know what you'd do until you found yourself in that situation."
Coronation Street continues on Thursday (August 30) at 8.30pm on ITV1.