A woman will receive more than £800 if she wins a bet that her fourth child will be born on Friday to maintain a sequence of Christmas births.
Wendy Legister, from Worcestershire, has given birth before on 26, 27 and 28 December and has placed a £29 bet at 29/1 that the run will be extended.
The 38-year-old, from Kidderminster, is convinced she will have the baby on 29 December, bookmakers William Hill said.
It said it was "perhaps the most unusual festive flutter" of the year.
Spokesman Graham Sharpe said the company was delighted to be able to oblige with her bet.
He added: "We (have spoken) to Wendy a couple of times over the past few days and there will now be a pregnant pause while we wait to find out whether she will deliver herself both a new baby and a win on Friday."