Jason Day has explained why he'll miss the birth of his fifth child if they arrive during the Tour Championship - because he's been told to by his pregnant wife Ellie.

Ellie Day is due to give birth to the couple's fifth child in just under two weeks, which would usually mean a golfer is on high alert to drop his clubs and head home if word comes of an early arrival.

The former World No.1 missed the 2012 Open Championship to attend the birth of his first child Dash, but has been given orders this time around to concentrate on winning the Tour Championship.

Days says he's hoping his wife will not give birth until after the PGA Tour finale at East Lake, but even if she does she has told him to stay in Atlanta and finish the tournament.

“I'm just hoping that Ellie holds out another week or two weeks and I can be there and spend some time with my family,” Day told Golf Digest. “I think if this was my first, I’d be a little bit more nervous about it.

“She (Ellie) said, ‘You're not likely to make it back in time if I do go into labour. We're having a home birth. She said I may as well just play the tournament and try to win.”

It's a tough task for Day to come out on top in the Tour Championship though, as he starts the even nine shots behind Scottie Scheffler in the adjusted leaderboard.

“I've got to play some of the best golf have ever played and I need a little bit of help, too,” said Day.

“It's nice in a sense that at nine shots back, you can just go out and play and not have to worry about being around the lead. I'm hoping to rekindle some of that form and iron play from earlier this year and continue to drive it well.”

Day has had something of a renaissance this season, winning his 13th PGA Tour title with victory at the Byron Nelson and finishing tied second at the Open Championship last month.

And big leads can be overcome at the Tour Championship, as Rory McIlroy showed last year.

"I fell 11 shots behind Scottie after two holes of the tournament," McIlroy recalled of last year. "So if I can come back from 11 shots, I feel like everyone in this field should feel like they have a chance to win."