The 25 year old's character, Tina McIntyre, is involved in a surrogacy storyline, and the prosthetic pregnancy belly and gown hint that the time has come for her to meet her baby.
The brunette actress was at one point hunched double as she waddled along the soap's famous cobbles.
Childbirth action: Michelle wore a hospital gown for one of her scenes, which could be one of her last for Corrie
Speaking to ITV, Michelle revealed it's her biggest storyline during her six year tenure with the award winning soap.
'It's the biggest storyline for Tina yet, expect lots of juicy twists and turns to come,' she said.
Prettiest pregnant girl in Weatherfield: Michelle Keegan in character as Tina McIntyre
A source told The Sun that Michelle's decision to quit the top soap was not related to her boyfriend being based hundreds of miles away.
They said: 'This is totally Michelle’s decision and what is best for her career. It has nothing to do with wanting to spend more time with Mark.'
The actress said: 'I have had the most amazing 6 years at Coronation Street and it was such a difficult decision to leave. But I felt it was the right time for me to make the next step in my career.
'I will miss Tina and will always be grateful to ITV and Coronation Street for giving me such an amazing role to play for my first ever acting job. Most of all I will miss the amazing people who work on the show, my acting colleagues, cast, crew, producers and writing team. I have met people who I know will be friends for life.
'I am very excited about what the coming months hold for Tina and what the future has in store for me.'
Daunting storyline: Michelle has been involved in a surrogate storyline and is about to film childbirth scenes
A few hours after her announcement, she took to Twitter to thanks fans for their support: 'Getting all emotional reading your tweets... It was such a hard decision! Thankyou for all your support. Honesly it means so much.'