Doctors in Canada have delivered a frail but healthy boy from a brain-dead woman kept on life support for weeks, the infant's father wrote in a blog post.

Dylan Benson, 32, had been keeping a running online account of his emotions as he grieved for his wife and prepared for the birth of his son.

Doctors, who had hoped to keep the pregnancy going for 34 weeks, delivered the boy via Caesarean section at the weekend after 28 weeks.

"On Saturday evening, my beautiful and amazing son, Iver Cohen Benson, was born," Benson wrote in a post on Monday, shortly after the birth at a hospital in Victoria, British Columbia.

Benson added that the day after delivering the baby, doctors disconnected the life support equipment that had allowed his wife's body to incubate their unborn son.

"On Sunday, we had to unfortunately say goodbye to the strongest and most wonderful woman I have ever met," he wrote.

Robyn Benson, 32, collapsed in late December when she was 22 weeks pregnant, and was declared brain-dead from a blood haemorrhage.

The moving online odyssey was followed by readers who donated Canadian $152,000 ($A152,400) for Iver's medical bills.

Benson wrote that his son was doing well despite being several weeks premature, and posted a photo in which he is shown holding the tiny child in the hospital's intensive care ward.

The post was captioned "Immensely sad, but incredibly proud."

"As to be expected, it will still be a bumpy ride for he and I as he continues to grow under the care of the wonderful staff at the hospital."

Amid the joy of his son's birth, the newly widowed Benson wrote that he grieves the loss of his wife.

"I miss Robyn more than words can explain," he said.

"She will live on forever within Iver, and in my heart.