Robyn Benson, from Victoria, Canada, collapsed at home after complaining of a piercing headache.
Nothing could be done to save her and she has been declared brain dead.
Doctors are now trying to keep her body alive for another seven weeks, so the baby can be safely delivered by Caesarean section.
As he keeps a bedside vigil, Robyn's heartbroken husband, Dylan, has spoken about his mixed emotions as he prepares to become a father.
He told told CBC: "On one hand, I can't wait to meet my son and try, and give him the best life possible and try my hardest to be a great dad for him. On the other hand, I know that the day or the day after he is born will be the day that I have to say goodbye to Robyn.
"Pretty much her body is doing everything but her brain isn't there anymore."
The couple, who had been high school sweethearts, married in July and were eagerly looking forward to the arrival of their first child.
When the baby is born, Dylan plans to call him Iver - a name the couple had chosen before Robyn's sudden illness.
On the morning that she suffered the brain haemorrhage, Robyn had woken with a piercing headache and asked her husband to go out and buy painkillers.
When he returned, she was slumped unconscious in the bathroom.
She was rushed to hospital but the following day, on December 29, she was declared brain dead.
A You Caring fundraising site has been set up to help Dylan, who will be welcoming a baby into the world at the same time as burying his wife.
In an update on Iver's progress, Dylan posted a message on the site saying how touched he was by the support.
He added: "We had another ultrasound today and things are still looking good for Iver, and Robyn is still holding on strong."
Money raised through the fund will be used to pay for baby supplies, daycare, housing and an education fund for Iver.
Dylan said: "It is very difficult to know that our son will grow up never meeting his wonderful mother, and that we will have to say our goodbyes to Robyn within hours of seeing Iver for the first time."
Suggested For You
SUBSCRIBE AND FOLLOW
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements.Learn more