Two-time Olympic gold medallist Rebecca Adlington has announced that she is expecting her first child with husband Harry Needs.

The 25-year-old, who retired from swimming in February last year, married her long-term partner, who is also a swimmer, three months ago.

"The due date is June 4 so, yes, we must have conceived on the first day of our honeymoon in Venice," Adlington told Hello! magazine.

"Thank goodness everything is okay [after the first scan]. It was such a relief to see the heartbeat. I think you feel such a responsibility as the woman because you are the one looking after the baby. So Harry was more excited but I was more nervous."

Adlington, who has a total of 17 international swimming medals, has also revealed that she wants a water birth.