Appendix 5: Non-invasive prenatal screening

Non-invasive prenatal screening (NIPS) is a way of determining the risk of the fetus having certain chromosomal abnormalities. Small fragments of circulating DNA in a pregnant woman’s blood are analysed. These fragments are free floating and not within cells, unlike most DNA, which is found inside a cell’s nucleus. They are therefore known as cell-free DNA (cfDNA). During pregnancy, a mixture of cfDNA from the woman’s cells and cells from the placenta are found in the maternal blood. Evaluation of the cfDNA from the placenta allows screening for certain genetic abnormalities. NIPS can be performed from the 10th week of pregnancy.

NIPS can be used to screen for chromosomal disorders such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome). The accuracy of the test changes depending on the disorder in question.

NIPS is not appropriate when there is fetal abnormality or significantly raised nuchal translucency (NT).

Note: NIPS is not part of the publicly funded antenatal screening for Down syndrome and other conditions. NIPS is currently a user pays, non-scheduled test. If this changes, this section will be updated as appropriate.

If a woman chooses to have NIPS (non-funded) as their primary screening test, knowledge of dates is required.

The woman should still proceed with a scan at 12 to 14 weeks gestation for assessment of fetal anatomy and for other benefits. However, NT measurement (and combined screening assessment) is not recommended in women with a previous NIPS result (Note: The NT should still be measured if it appears increased, and Fetal Medicine or other local equivalent specialist referral should be offered if NT is ≥3.5 mm.).

A woman may choose to have NIPS (non-funded) following combined screening assessment.

For further information, see:

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