Lucy Lintott, 24, the country's youngest person to battle motor neurone disease is believed to be the first to fall pregnant post-diagnosis.
She made the incredible announcement on Friday afternoon on her social media accounts, sharing a picture of her and fiance Tommy Smith cradling her 'bump'.
Writing on Twitter, Ms Lintott said: “We’re delighted to announce that early next year we’ll be bringing our baby boy into the world.”
Lucy was diagnosed in 2013 with MND, aged just 19.
Doctors told her she might have just four years to live, and she feared she might never be a wife.
The inspirational campaigner threw herself into fundraising for charity MND Scotland, so far raising more £200,000 to help find a cure for the debilitating disease.
It is understood that the baby is due in February, with the couple expected to exchange vows in a ceremony next year.
Speaking to the Evening Times, Lucy said: “They told us there are no known cases anywhere of someone with MND becoming pregnant.
"But my womb is unaffected by MND so in theory I should have a normal pregnancy and be able to have a natural birth."
She added: "I see a consultant and get scanned once a month, and the doctors have said they will just have to play things by ear - just like any other mum-to-be.
“If there are complications then we will deal with them - just like anyone else."