Non-invasive prenatal screening (NIPS)
Non-invasive prenatal screening (NIPS) is the most sensitive and specific screening test for the common foetal aneuploidies. Due to advances in genomic technologies, we can detect the presence of foetal cell-free DNA, derived from the placenta, circulating in the maternal blood to screen for common foetal aneuploidies. The preferred nomenclature changed from NIPT to NIPS ('S' for screening) to emphasise that utilising a cell-free DNA approach is a screening test and not diagnostic. The purpose of prenatal screening for aneuploidy is to provide an assessment of the woman's risk of carrying a foetus with one of the more common foetal aneuploidies. This is in contrast to prenatal diagnostic testing for genetic disorders, in which the foetal chromosomes are evaluated for the presence or absence of abnormalities in chromosome number, deletions and duplications, or the foetal DNA is evaluated for specific genetic disorders.</p
Recent international guidelines (ref.1-4) advocate the following:
- NIPS be offered to all pregnant women regardless of risk.
- Patients should have the opportunity to make an informed choice to decline or accept testing.
- Pre- and post-test counselling regarding the benefits, risks and limitations is essential.
Current Screening options available
Lancet Laboratories offer First Trimester Down Syndrome Screen, Second Trimester Down Syndrome Screen and NIPS. Each screening option has relative advantages and disadvantages. It is important that obstetriciangynaecologists and other obstetric care providers be prepared to discuss not only the risk of aneuploidy but also the benefits, risks, and limitations of available screening tests. Screening for aneuploidy should be an informed patient choice, with an underlying foundation of shared decision making that fits the patient's clinical circumstances, values, interests, and goals. All patients should still be offered a second-trimester ultrasound for foetal structural defects, since these may occur with or without foetal aneuploidy (ref.2).