Maternal weight’s role in risk calculation for Down syndrome and other conditions

From 1 July maternal weight must be provided on the screening request form.
From 1 July maternal weight must be provided on the screening request form.
Maternal weight is an important part of the risk calculation for screening for Down syndrome and other conditions and the National Screening Unit (NSU) is changing the requirement for maternal weight to be provided on the screening request form.

Currently, if the weight is not provided, a default weight is entered to complete the risk calculation. This approach has been found to be too inaccurate.

From 1 July, all requests for antenatal screening for Down syndrome and other conditions must provide a maternal weight on the request form for a risk report to be generated. If it’s not provided, the screening laboratory will write to the practitioner asking for the maternal weight, which can then be provided by phone or email.

To best record an accurate maternal weight:

  • weigh as close to the time of screening as possible
  • use calibrated scales
  • keep clothing consistent (eg, shoes off, light clothing).

To provide a weight or to find out a risk result: 

  • for Taupo and north call LabPLUS on 0800 522 7587 or email Lablink@adhb.govt.nz
  • for south of Taupo call Canterbury Health Laboratories on 0800 843 522 or email info@chl.co.nz.

An example of how the information provided can change the risk calculation can be found on Page 54 of the Guidelines for Health Practitioners.

Further information on weight in pregnancy can be found here.

Providing all the information asked for on the request form will assist with a high-quality risk report. This includes details of IVF pregnancies, ethnicity, smoking status and information on previous pregnancies. Request forms can be ordered by emailing newbornscreeningresources@adhb.govt.nz

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Page last updated: 30 June 2015