The 26-year-old, who leads Sergio Garcia by almost 1,000,000 points at the top of the standings in the battle to become European No 1, has chosen to stay with partner Clare rather than travel to Close House.
The Englishman said in a statement: “I wanted to give myself every chance of playing this week, but being there at the birth of your child is a special moment in anyone’s life and I would not want to miss it.
“Lee Westwood has done a great job as tournament host of the British Masters and I want to wish him, Sky Sports, and everyone else involved all the best for what should be a great week at Close House.
“I look forward to returning to playing soon and hopefully I can have a strong end to the season and compete for the Race to Dubai title.”
Meanwhile, the European Tour will return to Belgium for the first time in 18 years when Thomas Pieters hosts the Belgian Knockout – an innovative new event which incorporates a head-to-head strokeplay knockout format – at Rinkven International Golf Club in Antwerp next May.
Pieters, who claimed four points in last year’s Ryder Cup at Hazeltine to become the most successful European rookie in the history of the biennial contest, unveiled the tournament, which will be part of the 2018 Race to Dubai, at a press conference.
The opening two rounds will follow a familiar strokeplay format for 36 holes, before the leading 64 players then go head-to-head in knockout strokeplay matches contested over nine holes.
“I think it’s going to be exciting,” said Pieters. “We are going to see an innovative new format and it will make it really exciting for people who come along to watch and also for people watching it at home on TV.”