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The Government is expected to announce a full-scale screening programme for Down syndrome testing because the current tests put unborn babies' lives at risk.
An announcement on the project is expected in or before next month's Budget.
The head of a group set up to advise the Ministry
of Health on Down syndrome screening said yesterday that the current form of screening, without a blood test from the woman, was "unsafe, inequitable and should not continue".
The screening now relies mainly on maternal age and an ultra-sound check at 11-14 weeks of pregnancy of the depth of fluid in part of the fetal neck - called nuchal translucency testing.
Women deemed at increased risk from those checks can have diagnostic tests which involve taking a sample of either the fluid from within the sac around the foetus or tissue from the placenta. Around 3500 of these tests - amniocentesis and chorionic villus sampling - are done each year in New Zealand. They carry a 1-2 per cent risk of having a miscarriage.
A member of the advisory group, Auckland University maternal and fetal medicine specialist Professor Peter Stone, said more normal pregnancies may be affected by amniocentesis than Down syndrome detected and so the test should be stopped.
The advisory group's chairman, Dr Paul Harper, said common screening methods were less accurate resulting in too many women having the invasive tests and pregnancies being lost unnecessarily.
Women can, between weeks 14 and 20 of pregnancy, have a Down screening blood test, although it costs $75 and is not publicly funded.
After concerns were raised that the invasive tests were being done needlessly in some cases or without explaining the risk of miscarriage, the ministry wrote to thousands of health workers telling them maternal age alone was not a sufficient reason for the screening test and to provide better information to women.
The chance of having a baby with Down syndrome, a chromosome abnormality that results in intellectual disability and an increased risk of some physical problems including heart disease, rises steeply after the age of 35. At 20 it is 0.066 per cent; at 45 it is 2 per cent.
New Zealand's incidence of Down syndrome rose from 0.87 per 1000 live births in 1996 to 1.48 (80 Down babies) in 2002.
Health Minister Pete Hodgson has asked officials to advise him on how a nationally organised voluntary antenatal Down screening programme could be implemented. The manager of the ministry's national screening unit, Karen Mitchell, said this advice would be provided by October.
The aim of an organised Down screening programme would be to improve the quality and safety of screening, she said.