Northland and the West Coast had even higher death rate estimates, but only Counties Manukau's was "statistically significantly" above the average. This is because it has so many more births, making its estimates more certain and their margins of error sat above the average, whereas Northland's and the West Coast's margins straddled the average.
The committee called for further investigation - and three more years of data has confirmed Counties' "outlier" status. It is thought that other DHBs might join Counties once a few more years' data are in.
Last year the Counties Manukau District Health Board appointed a panel led by law professor and former Health and Disability Commissioner Ron Paterson to see what could be done about the area's high perinatal death rate, which affects Maori and Pacific people more than others.
The panel's wide-ranging recommendations for improvements in maternity care and family planning services are made public today.
Around 8500 babies a year are born to Counties Manukau women, of whom more than half are born to Maori or Pacific women and to mothers who live in poor areas.
The perinatal mortality review committee's reports indicate Counties Manukau women's perinatal death rate is 21 per cent higher than the national rate for 2007-2010. But when the data was adjusted to account for Counties Manukau's high rates of Maori and Pacific ethnicity and poverty, the difference virtually disappeared.
"What this means is that if Counties Manukau ... had the same ethnic and socio-demographic ... make-up as the rest of the country, then the perinatal death rates are likely to be similar," the committee says.
"Pacific and Maori mothers and socio-economically deprived mothers in the remainder of the country are at similar risk as those mothers in Counties Manukau DHB."
Delving deeper into the reasons for Counties Manukau's higher rate, researcher Dr Catherine Jackson says in reports for the health board that "it is not being Maori or Pacific that places you at higher risk. It is an increased odds of exposure to risk factors such as smoking, obesity, premature birth, etc."
But a new analysis for the Paterson panel by one of the national committee's researchers did discover that there may be something about living in Counties Manukau that pushes its rate up, although this was from a weaker statistical method.
"... the data do suggest that Pacific women and those living in the highest deprivation quintile are more likely to suffer a perinatal death in Counties Manukau DHB than similar women living elsewhere in New Zealand," the panel's report says.
"With the greatest number of births in New Zealand, a large population of Pacific women, and some of the highest deprivation neighbourhoods in the country, Counties Manukau carries the greatest burden of perinatal death in New Zealand.
"The ... district also has higher rates of some potentially avoidable types of perinatal deaths - such as those due to fetal growth restriction, perinatal infection and spontaneous preterm birth, and maternal conditions such as diabetes and pre-eclampsia.
"Some of these deaths can be prevented with optimal antenatal care, highlighting the need to improve how maternity care is provided to vulnerable women who live in Counties Manukau. There is an urgent need to mitigate the impact of underlying health and social risk factors and reduce the overall number of perinatal deaths in the region."
Dr Jackson identified the most important potentially modifiable risk factors as overweight and obesity, advanced maternal age, smoking, pre-existing high blood pressure, pre-existing diabetes and early detachment of the placenta.
Extreme prematurity is the leading risk factor for stillbirth and neonatal death. The perinatal classification includes late abortions, of which more than 80 per cent, both nationally and in Counties Manukau women, are because of congenital abnormality.
Dr Jackson says smoking in pregnancy contributes significantly to perinatal mortality in Counties Manukau independently of any other risk factors.
"If no Counties Manukau DHB women smoked during pregnancy the total perinatal mortality rate ... could be expected to decrease by 21 per cent for all infants and by 67 per cent for infants born to Maori women."
"Overweight and obesity in Counties Manukau DHB mothers is contributing to stillbirths in infants weighing 1500g or more. If all Counties Manukau DHB mothers had a weight in the normal range at conception, the total perinatal mortality rate - excluding terminations - could be expected to decrease by 12 per cent for all infants and by 26 per cent for infants born to Pacific women."
By ethnicity and gender, Maori women of child-bearing age have New Zealand's highest smoking rate at more than 40 per cent, and Pacific women the highest overweight/obesity rate at more than 60 per cent.
The thrust of the Paterson recommendations is that more must be done by the Health Ministry and the Counties Manukau DHB to reach out to the area's women with high and complex needs, estimated at a whopping 80 per cent of those giving birth. This approach is reinforced by the re-emergence this year of the area's chronic shortage of midwives. The shortage was previously said to have been ended by the recession, forcing midwives back into midwifery and had earlier led to the ministry allowing Counties Manukau to bring back funding for shared GP-midwife maternity care.
The DHB - praised by the panel for quickly grasping the need to deal with the problems once highlighted by the national committee - has appointed a taskforce to implement the panel's recommendations.
The panel wants the ministry to look at introducing a top-up payment for community midwives when they care for women with high needs, which would mirror the state subsidies paid for GPs' patients in poor areas.
It is critical of the shared care arrangement and concerned that some GPs don't have proper qualifications for maternity care, although it notes the use of shared care has dropped from 21 per cent of births, to 14 per cent.
Professor Paterson says that although there was no difference in perinatal mortality rates between shared care and other models of primary maternity care - such as care from community midwives or hospital midwives - "there is a sense that the model of shared care that has grown up in Counties isn't working consistently to meet the needs of mothers and babies. We see a place for GPs here, but they need to be suitably qualified for maternity care."
The panel echoes earlier reports on the importance of getting women into maternity care early, preferably before 10 weeks gestation - only 17 per cent of Counties Manukau women sign up by this point and 2.5 per cent have no pre-labour care at all - but can't provide definitive answers on how to do this.
The recommendations:
1. Counties Manukau District Health Board to appoint project manager to ensure recommendations implemented.
2. Consider incentives, such as free baby products, for women who attend full pregnancy assessment appointment before 10 weeks gestation.
3. DHB to review access to pregnancy-related ultrasound scanning.
4. Decide which kind of health worker is best to care for the most socially and medically vulnerable pregnant women.
5. Health Ministry to consider introducing incentive payments for community midwives who care for pregnant women with high needs.
6. Ministry and DHB to urgently review family planning services in Counties Manukau, ministry to increase funding and DHB to extend its own contraception and abortion services.
7. DHB to allow more clinical input in management structure of women's health services.
8. Improve Maori and Pacific access to maternity services.
9. Urgently implement a comprehensive integrated maternity information system.
Source: External review of maternity care in Counties Manukau
