Future dad Dan Carter tries to stay focused

Ever the professional, All Black Daniel Carter is trying to stay focused on this weekend's test match against England after saying publicly for the first time that he's going to be a dad.

The star-first five and his wife Honor made the announcement on Twitter today that they are expecting their first child.

"Thought it was time to share our exciting news.. @HonorCarter is 21 weeks pregnant! We are both very excited about being parents #BabyCarter", he said.

Carter is currently in London preparing for the All Blacks test against England at Twickenham, and his agent Dean Hegan said Carter was trying to stay focused on the game.

"He's concentrating on playing on Saturday (local time)," he said.

"I've spoken to him and he's obviously delighted and looking forward to it."

Carter would be back with his wife in New Zealand in mid-December, Mr Hegan said.

Honor Carter also tweeted her excitement: "Time to share our exciting news ... @DanCarter & I are expecting our first child! I am 21 weeks & we are both very excited :) #BabyCarter".

Former rugby league international Monty Betham was among those who passed on their congratulations on Twitter.

"2 highly motivated & successful people. Now you will have even more purpose in your lives. #Congrats. #TeamParents."

Carter and Honor, a former New Zealand Black Sticks hockey player, married last December.