Keri Young found out her baby suffered from anencephaly - a condition where the baby's brain doesn't develop properly - when she went for her 19-week ultrasound.
The baby girl, who they've named Eva, is expected to die within hours of birth.
The hospital gave Young and her husband Royce the option to induce early pregnancy but the pair decided that they would carry the baby to full term instead in order to donate her organs and give other sick babies the chance to live.
In a Facebook post, Mrs Young wrote: "For the next 20 weeks, I will feel her kick, have the hiccups and we'll be able to hear a perfect heart beating all while knowing we'll only get a few short hours when she's born.
"We had some pretty awful thoughts running through our minds... Everything from 'there's no way God exists' to 'we're going to spend all this money on pre-natal care and labour and delivery and not take the baby home'?"
But the couple were encouraged to go through with the pregnancy when her physician told her carrying Eva to term would be "the most selfless thing she'd ever do".
Their church pastor also told them that "In your daughter's short life, she might save 50 lives. She's going to be a busy girl."
In his own Facebook post, Royce Young said he was in awe of his wife's strength.
"There's another family out there hurting and hoping for a miracle for their baby, knowing full well someone else's baby will need to die first. Eva can be that miracle."
"I'm looking at Keri right now and I don't even have to ask.
"She's brave. She's incredible. She's remarkable. She's cut from a different cloth... And somehow, she's my wife."
Eva is due on 7 May.