Noninvasive prenatal testing: an overview

Australian health authorities recommend offering prenatal screening for fetal chromosome conditions, also known as aneuploidies (e.g. Down syndrome [trisomy 21]), to all pregnant individuals to support informed decision-making. Noninvasive prenatal testing (NIPT) is one of 3 types of prenatal aneuploidy screening tests available in Australia. NIPT requires a maternal blood test after 10 weeks gestation. Although it doesn't require an ultrasound, a 12- or 13-week ultrasound is recommended as it provides an opportunity for early diagnosis of major structural anomalies. NIPT is not subsidised by Medicare. It is important to take a patient-centred approach when discussing screening options. Patients should be encouraged to consider whether knowing the test result will impact their pregnancy decision-making or preparations. There are two main NIPT approaches: genome-wide and targeted. All currently available NIPT platforms perform well for detecting the common autosomal aneuploidies (trisomy 21, 18 and 13). NIPT has the highest true-positive rate (highest sensitivity) and lowest false-positive rate (highest specificity) among aneuploidy screening methods, however false-positive results can occur. Genetic counselling and confirmatory invasive diagnostic testing are recommended for patients with a high-probability NIPT result, especially if they are considering pregnancy termination.