Paris Fury, who is only seven weeks pregnant, said she believes revealing the news "inspired him to victory".
The mum, who openly revealed she suffered a miscarriage last year, said she thought for a long time about whether to tell her husband before his fight.
She told The Mirror: "I didn’t want to change his concentration or his mood, but when I got over there I realised nothing changes his concentration or his mood.
"We’ve lost children in the past, so God willing, I just hope we get to the end and we get a baby."
Setting off to arena. 👊👊 pic.twitter.com/CHVSyvEWsu— Paris fury (@parisfury1) November 28, 2015
The mum said the soon-to-be dad-of-three replied with: "Really? Really? I asked God for a child and now I have one.
"Hopefully tomorrow night I will win, then my world will be complete."
Paris, who has daughter Venezuela, six, and Prince, four, with Tyson Fury, said her husband is keen on expanding their family.
She added: "Tyson has said he wants 10 kids and I’d be happy with that. God willing we’ll get as many as God gives us."
The couple, who wed in November 2008, reportedly returned home from the fight in Germany via car and ferry because they didn't want to take any risks over Paris' pregnancy.
The source said, according to the Mirror: "Paris did not want to fly. She is pregnant and, although it is early days, they did not want to take any risks."