More midwives are being investigated for serious mistakes than workers in any other medical profession.
A snapshot included in the Health and Disability Commissioner's latest annual report (PDF, 2.5MB) showed almost a quarter of the cases before the director of proceedings - who decides whether to prosecute - concerned midwives.
Six cases had been referred at the time, compared to two for nurses and two for obstetricians and ahead of any other speciality.
About 10 percent of all Health and Disability Commissioner investigations involve midwives and and about nine per cent of breach findings relate to midwifery care.
About 3000 midwives are registered in New Zealand, compared to about 52,700 nurses, 14,700 doctors and 2200 dentists, according to the Health of the Health Workforce Report published early last year.
However, Health and Disability Commissioner Anthony Hill said it would be wrong to say midwives were over-represented.
"It's not a surprise to see complaints in midwifery appearing in the senior and serious end of the scale, because the nature of the harm that can occur when it does occur is very significant."
Mr Hill said the number of serious cases had remained relatively static. Last year he got 62 complaints about midwives, which was low in comparison to the 60,000 births each year.
The latest figures from the Perinatal and Mortality Review Committee (PMMRC), which reviews the deaths of babies and mothers, showed the rate of baby deaths shortly before or after birth was the lowest since reporting began 10 years ago, he said.
"New Zealand has been improving significantly over time ... and we compare well with international comparators also.
"Which indicates that there's an independent view that says the midwifery model in New Zealand is a safe and sound model and is working well and the stats very much support that," he said.
Figures show there is a problem - charity
The charity Action to Improve Maternity supports parents with maternity care related concerns.
Its founder and head, Jenn Hooper, said the figures showed there was a problem.
"If it really is a matter of the nature of the beast and this is the potential outcome, explain to me how come so many breaches are upheld in that sector, because breaches don't come unless there is substandard care," she said.
Ms Hooper said the PMMRC's figures showed the death rate for newborns has remained stagnant for more than a decade.
"The PMMRC themselves have stated that it is an area of concern and that they need to look specifically at why we haven't improved in that particular area in all this time, when other countries have," she said.
The figures showed that while there has been a statistically significant reduction in the number of stillbirths, the trend in overall perinatal mortality was not statistically significant.
Ms Hooper said families were struggling to get the Health and Disability Commissioner to investigate complaints.
However, Mr Hill said every complaint was carefully assessed, but only the most serious were investigated.
Last year the HDC received nearly 2000 complaints, completed 80 formal investigations and found 60 cases where patients suffered serious breaches of care.