The actress, who plays Michelle Connor in the ITV1 soap, admitted that she has been contemplating marriage for a while and will be organising a ceremony for 2012.
Speaking at the British Soap Awards, she told The People: "We've been thinking of marriage now, we will do it next year because we'd like to do it really soon."
Hollyoaks actor Lomas added: "We were thinking about it before, then Kym got pregnant."
The couple welcomed new daughter Polly in March. Marsh said: "This is our first night away since we had her. My mum has her and I've driven her mad ringing up to check, I've rung about 15 times."
Marsh recently confirmed that she will return to Coronation Street in September following maternity leave.