Screening for Down syndrome and other conditions - information for practitioners

image of pregnant lady holding her stomach
Options include first and second trimester screening.
The National Screening Unit (NSU) is responsible for monitoring and evaluating antenatal screening for Down syndrome and other conditions.

The screening options include:

  • first trimester combined screening (nuchal translucency (NT) ultrasound scan and maternal serum) or
  • second trimester screening (maternal serum).

For every 1000 women having screening, approximately 50 will receive an increased risk result and approximately two will be diagnosed with a baby with Down syndrome or another condition.

One of the areas that is reported and monitored is the number of women not completing screening. When women have a NT ultrasound scan in the first trimester, they are entering into the screening pathway, which includes information from the ultrasound, demographic information and a maternal serum (blood test) to generate a risk result.

Table 1 shows volumes for first and second trimester for the 2012 year and the numbers of incomplete screens. A high number of incomplete screens for the first trimester were due to an NT ultrasound scan being received by the laboratory but no maternal serum and vice versa. This equates to around 6000, or 13 percent of women who commenced screening but did not complete screening and did not have a risk result calculated.

Practitioners can support women by talking with them about the screening pathway and what it means to have an NT ultrasound scan. The scan can detect anomalies, is combined with maternal serum and is part of antenatal screening for Down syndrome and other conditions.

If a maternal serum has been received by the screening laboratory, a letter is sent to the practitioner to inform them that the woman has started on the screening pathway and that an NT ultrasound scan is still to be received. At 13+ weeks if a scan has not been received, the screening laboratory phones the practitioner to find out if a scan has been performed. If the practitioner fills out the request form and includes where the scan may be performed (the green shaded area at the bottom of the laboratory request form), the laboratory can ring the radiology practice directly.

​volume of antenatal screens for down syndrome and other conditions 2012


​For further information on this screening please visit Practitioner guidelines can be found here.

For further information from the screening laboratories contact:
LabPLUS at Auckland District Health Board (Taupo and North)
Canterbury Health Laboratories at Canterbury District Health Board (south of Taupo)


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Page last updated: 29 April 2014