First-time mums giving birth on the North Shore are more likely to undergo a caesarean compared to a woman living in Counties Manukau.
The Ministry of Health has ordered a review into why there is such a wide variance between caesarean rates at hospitals across the country.
A new mum's chance of undergoing a caesarean ranged from 9% in Waikato to 26% in Wairarapa.
The national average was 15.4 per cent and based on first-time mothers aged between 20 and 34 with no known complications.
Auckland mothers from Waitemata, 17.6 per cent, and Auckland district health boards, 16.2 per cent, were above average.
About 15 per cent of women giving birth in Counties Manukau underwent caesareans in 2009, up from 12 per cent the previous year.
However, Jenn Hooper, spokeswoman for Action to Improve Maternity, slammed the results and review as meaningless.
''With caesareans, unless they are actually leading to a lot of deaths do we actually care?
''Caesarean rates are going up all over the world, they have been for a long time.''
Rather than measuring how babies are delivered, the Government should measure the health of a newborn, she said.
''You can't just take one statistic and run with it.''
Hooper's daughter Charley, 7, suffered a massive brain injury after midwives botched the natural birth by failing to clear her daughter's airway.
Midwives have welcomed the Ministry's review.
College of Midwives chief executive Karen Guilliland said it could help determine a national guideline on when to intervene in birth.
''We want to understand why is it that some places women will mostly have a normal birth and some places they won't,'' she said.
The differences in caesareans rates were probably related to ''practice, protocol, tradition and culture'' of a region, rather than the actual women, she said.
The maternity indicators are for healthy, first-time mothers aged between 20 and 34.
Measuring this group of mothers reduced the risk of a region's demographics influencing the results, she said.
''You might have a population of women who are older and have medical conditions and you would expect their outcomes to be slightly different, although we standardised most of that.''
This group of healthy, new mothers were also more likely to be disadvantaged by too much intervention.
''Medical intervention is a lifesaver generally, but it can, if used unnecessarily, cause more problems that it can solve.''
The national average caesareans rate has remained stable against 2009.
National rates of natural births increased slightly between 2009 and 2010, while there was a nationwide decrease in the rate of instruments such as forceps being used during labour.
The Ministry of Health did not respond to questions relating to the review.
Caesareans are not available on request in New Zealand hospitals and are only performed when the safety of the women or her baby are at risk.
C-section by DHB (rate %)
Counties Manukau 15.2
National Average 15.4
*percentage of caesarean section among first-time mothers aged between 20 and 34 with no complications
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