The latest published national statistics only go up to 2011, when 24 per cent of births were caesareans, an increase from 22 per cent in 2002.
At National Women's, 17 per cent of births were "elective" caesareans last year and 18 per cent were emergency caesareans. Electives include those planned because of risks to the baby, and an unknown proportion - no one has done the research to find out - that are thought likely to be medically unnecessary, such as the "too posh to push" mothers.
The report's authors express a note of alarm: "The caesarean section rate, 34.7 per cent, is the highest it has ever been at NWH [National Women's Health, previously National Women's Hospital]. The most common reason for caesarean section is repeat caesarean.
"Research evidence is clear that repeated caesarean sections are strongly associated with adverse maternal outcomes ..."
There is some evidence that the rate increase is linked to rising obesity and the increasing age at which women are giving birth.
The elective caesarean rate at National Women's was highest (35 per cent) among women who hired a private obstetrician and lowest (9 per cent) among those booked with an independent midwife. The report suggests one reason for this may be women seeking out an obstetrician who is willing to do an elective caesarean.
"In 2014, a private obstetricians' governance group has been formed which, in part, may assist with the clarification of such drivers."
National Women's Health director Dr Sue Fleming said it was hard to know how many caesareans were medically unnecessary because the recorded information was in some cases insufficient to make a retrospective judgment.
Maternity Services Consumer Council co-ordinator Lynda Williams said that although caesareans were sometimes necessary for the health of the baby, there was now evidence linking the operation to an increased risk of allergies and chronic diseases later on. This was thought to arise because the child was not exposed to the normal bacteria of the mother's birth canal which aided normal development of the immune system.
"If caesarean sections are linked to these chronic diseases then we have got to stop doing so many and start telling mothers that this is the risk."
Disappointed, but procedure safest for baby
Tania Eastlake is disappointed that her son Charlie was born by caesarean surgery, but knows that for his safety it was the only option.
Charlie was born in the early evening on Friday, July 11 at Middlemore Hospital in an emergency delivery. This was soon after fetal monitoring had detected he was becoming distressed.
Ms Eastlake, 31, and her partner Simon Eves, who live in Papakura and are both photographers, went to the hospital in the early afternoon of the Friday, when she was 38 weeks pregnant. Her labour had begun that morning and was progressing rapidly.
"I had planned to have a natural birth but was fully dilated by 2.30pm. He had got stuck quite high up and he was posterior, facing the wrong way. It was decided I would have to have a caesarean section because he was too far up for forceps or ventouse.
"I was disappointed. I didn't want to have a caesarean section, but obviously the priority was Charlie and making sure he was fine. He was getting quite distressed because I was pushing and he was stuck."
"It was pretty quick. I went to theatre just after 5 and he was born at 6.
"Everyone was fine, I've recovered really well.
"Those first couple of days after the caesarean section were hideous. You can't move, you're quite restricted getting up and down and handling a baby.
"It takes a while for feeling to come back into your legs, you've had quite major surgery and you're trying to deal with a newborn.
"My tummy is still a little sensitive. If I move too quickly or pick up Charlie in his capsule and it's a bit too heavy you can definitely feel it.
"Obviously I'm going to have a scar forever."
The couple hope to have more children and Ms Eastlake hopes it will be a straightforward birth next time.
