The actress, who plays Michelle Connor in the ITV1 soap, went back to work last month following the birth of daughter Polly in March.
Viewers will see Michelle arrive back in Weatherfield next month with Ciaran, played by Keith Duffy, who announces that the couple are engaged.
"Although I kept in touch with people like Beverley Callard (Liz McDonald), Ali King (Carla Connor) and Antony Cotton (Sean Tully) when I was off, I felt nervous going back, as I had big scenes to film," Marsh told The Mirror.
"But there are other cast members that have small children and they've come back to work when their babies are six months old, and it's the same for me. Plus we have a nanny and Jamie [Lomas, fiancé] has finished Hollyoaks now, so he's around more, too.
"When Michelle comes back, she's helping Carla out due to what she's been through. Carla wants to be free of Frank and the only way out she can see is to drop the rape charges. Meanwhile, Michelle decides that she wants to get married in Weatherfield rather than the Bahamas. But nothing ever goes right for her – she's very unlucky in love."
Marsh recently admitted that she will miss Duffy, who will leave Coronation Street in a dramatic Christmas storyline.