Difficulty in achieving proper informed consent for a complex screening test and the varying phenotypic outcomes leaves pregnant women in a precarious situation when results are abnormal
The combined first trimester screening test for Down syndrome, involving a nuchal translucency scan and biochemistry at 11–13 weeks, improved detection rates to 90% when compared with the sensitivity of screening by age‐related a priori risk of around 30% for a false positive rate of 5%.1 The advent of non‐invasive prenatal testing (NIPT) in 2010 as a screening test for the common trisomies was revolutionary, with sensitivity, specificity and detection rates unmatched by the combined first trimester screening programs. NIPT was found to achieve a detection rate for Down syndrome of 99.7%, with a false positive rate of 0.04%.2 However, some NIPT providers now additionally offer extended panels and low resolution whole genome sequencing (WGS) including sex chromosome aneuploidies, rare autosomal aneuploidies, and subchromosomal deletions, duplications and recurrent microdeletions. This comes at a cost of a higher false positive rate and lower positive predictive value.3 Moreover, the expanded panels and WGS NIPT raise issues of clinical utility and ethical concerns.4,5
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