They are calling her their ''shock daughter''.

Thomas Jones and Erica Gunther have the ultimate souvenir of their New Zealand holiday.

Mr Jones (23), from England, and Ms Gunther (22), from the United States, had been in New Zealand for only a few weeks when they had the biggest, and best, surprise of their lives.

The couple met in 2011 when Ms Gunther was working as a teaching assistant in Mr Jones' home town, Kettering, in England.

However, visa difficulties in their respective countries kept them apart until they reunited properly in New Zealand in February for a year-long working holiday.

''Erica's ankles were swollen for an unnaturally long time after we arrived. A few weeks later, she was getting pain in her hip, which a doctor diagnosed as hip bursitis and told her to ice it and rest for 10 days,'' Mr Jones said yesterday.

''I thought it might be a burst appendix or, maybe, irritable bowel syndrome,'' Ms Gunther said.

''But, a week later, we were staying at the backpackers in Wanaka when I woke up with severe cramps in my lower abdomen.

''When they told me I was pregnant at the Wanaka Medical Centre I just thought 'Oh, my God'. I had no idea. There was no bump at all,'' Ms Gunther said. For Mr Jones, it was an even bigger shock.

''I was in the waiting room for over an hour and people kept coming in and were being turned away at reception. I was worried, because I thought something must be really wrong with Erica.''

''Then, 10 minutes before the baby was born, the doctor got me from the waiting room and said I was about to be a father. Before the air ambulance had a chance to arrive, she had given birth to our shock daughter, Laurelin.

''It was such a huge shock, because Erica didn't show at all and didn't even know she was pregnant. She had no bump and the doctor didn't even realise it the week before when examining her hip.

''Up until the day Laurelin arrived, she was cleaning, making beds and swimming in Lake Wanaka almost daily, all the while having no idea she had a baby girl inside her tummy. Laurelin was full term and weighed 7lbs 2oz. [3.23kg]''

Their families back home in New York and Kettering were equally surprised at the news.

''They didn't believe us,'' Ms Gunther said.

The couple married on the Lake Tekapo foreshore on May 13 and moved to Dunedin earlier this week, in the hope of Mr Jones, a graphic designer, finding some kind of work.

''We want to be a family and live in the same country. We'd really like to stay in Dunedin, if we could.''