About 3am today and halfway through a contraction, Sulia Toomalatai's midwife Ady Priday asked her if she wanted to hear something funny.



"I said, 'oh, can you hold on a second?'," Toomalatai said.



Priday went ahead and told her anyway that the baby she was about to deliver at Middlemore Hospital had been nominated as Auckland's 1.5 millionth resident and did she mind the media arriving in a few hours to document the milestone?



"It was quite a surprise being told in the middle of contractions," Toomalatai said.



"I didn't realise that's how many people we had in Auckland."



Four days overdue and just shy of 10lbs, Ramonah Patience Toomalatai was eventually born at 4.36am. The little girl is Sulia and Tutasi Toomalatai's third child.



Priday, who had also delivered the New Zealand Samoan couple's four-and-a-half-year-old son, said that after the initial shock Sulia and her husband Tutasi were "very excited".



"I'm suspicious that the baby knew all along, though.



"I guess she must have known she was the 1.5 millionth."



Tutasi, who works for Tip Top in Manurewa said he was "so proud" of his new baby and had taken two weeks off work to help at home.



Four hours after she was born a bevy of guests, including Mayor Len Brown came to visit to mark the occasion. Brown walked in carrying a hamper full of nappies and All Black-emblazoned baby clothes.



Brown's communications manager Glyn Jones said the maths they had used to calculate who would be the 1.5 millionth was based on data from the past five years.



Auckland's population has grown at a rate of 1.6 per cent each year. Statisticians took that figure forward, divided it by 12 and discovered that by the end of January or start of February it would hit the milestone.



Statistics New Zealand also calculated it was far more likely to be a baby rather a migrant and so planners nominated Middlemore Hospital in south Auckland which has the city's biggest maternity ward. About 6900 babies are born there each year.



Sulia said she hadn't told her son or seven-year-old daughter about their new sister's celebrity status but it would inevitably be part of her life - even if it was just marked by a certificate that she could hang on her wall and tell friends about.



"It's a nice story to tell her, it's part of her life right from today."



Projections show that by 2012, for every 100 people in Auckland, 53 will be European, 27 will be of Asian heritage, 17 will be Pacific Islanders and 12 will be Maori.



The figures add up to more than 100 because people can identify with more than one ethnicity.



Statistics New Zealand senior demographer Kim Dunstan has said that doesn't mean the rest of the country would be the same sort of cultural melting pot.



"Auckland does have slightly higher birth rates than other regions, and partly that reflects a younger population."



"And of course fertility rates are generally higher for Maori and Pacific populations than they are for Asian and European populations. Migration is also an important contributor to growth, particularly in Auckland."



Brown has said the city needed to think about how it would cope with its growth with the number of people travelling to and from work each day expected to jump from 1 million to 1.26 million by 2031.



The city also needs another 226,000 in that time meaning an average of 10,590 new houses needs to be built every year.



The proportion of people living in the super city will increase from 34 to 38 per cent with another 90,000 school-age children.