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Our tertiary centre experienced a relatively smaller decline in prenatal diagnostic procedures compared with national figures, largely due to an increase in testing for ultrasound abnormalities. Our results demonstrate the increasing contribution of first trimester ultrasound in the detection of fetal abnormalities in the cell-free DNA era and the continued viability of specialist training in invasive procedures.

Non-invasive prenatal testing (NIPT) for fetal aneuploidies by massively parallel sequencing has transformed the approach to prenatal care. The presence of circulating fetal cell-free DNA (cfDNA) in maternal plasma, which is derived primarily from the placenta, is the basis of this test.1 Studies comparing NIPT to serum or combined screening have shown that NIPT outperforms these screening options in trisomy detection and has significantly lower false positive rates. 2-4 Biological causes of false positive NIPT results may include maternal mosaicism (primarily sex chromosome mosaicism), confined placental mosaicism, co-twin demise, maternal malignancy and maternal copy number variation. 2,5 Here, we present a case of a nonstandard NIPT result involving a large and pathogenic partial duplication of chromosome 18q first indicated by NIPT. Subsequent prenatal diagnosis confirmed the presence of the duplication in the fetus, which was inherited from the phenotypically normal mother who carried the same chromosomal imbalance, but in mosaic form. A review of the NIPT data indicates that maternal mosaicism for this large segmental imbalance is sufficient to cause a false positive NIPT result in subsequent pregnancies, in the absence of the imbalance being transmitted to the fetus. Therefore, maternal mosaicism for large segmental copy number abnormalities may be yet another rare cause of false positive NIPT results, which further highlights the need for confirmatory invasive testing whenever an abnormal NIPT result is returned.The patient was a 38-year-old G3P2 woman who underwent first trimester combined screening. Risks for trisomy 18 and trisomy 21 were calculated at 1:13,100 and 1:1,690, respectively. No further investigations for Down syndrome or trisomy 18 were recommended on the basis of these low risk results. A fetal anomaly ultrasound scan at 20 weeks of gestation identified an isolated aberrant right subclavian artery. The sonologist counselled a low risk for chromosome abnormality 6 but informed the patient of the option of NIPT and amniocentesis. The patient was not referred for formal genetic counselling and pursued NIPT independently.Maternal venous blood was collected for NIPT at 20 + 6 weeks of gestation, and testing was performed by Natera Panorama ™ test, which is a targeted, multiplexed, single nucleotide polymorphism (SNP)-based NIPT assay. 7 The NIPT returned an unexpected finding with no result for chromosome 18 because of an 'atypical finding outside the current scope of the test'. The atypical finding was a suspicion of a partial duplication of chromosome 18. To help direct follow-up testing, a request was made for genomic or cytogenetic breakpoint information but was declined on the basis that the information being sought was outside the current scope of the test. Genetic counselling was arranged, and the patient elected amniocentesis at 22 weeks of gestation, at which time a small ventricular septal defect on ultrasound was also noted. As no positional information for the suspected duplication...

Three decades ago, the observation that first trimester fetuses with excess fluid accumulation at the back of the neck were more likely to be aneuploid, gave rise to a new era of prenatal screening. The nuchal translucency (NT) measurement in combination with serum biomarkers and maternal age, resulted in the first trimester combined screening (FTCS) program. The introduction of noninvasive prenatal testing (NIPT) over the past decade has introduced the option for parents to receive highly sensitive and specific screening information for common trisomy from as early as 10 weeks gestation, altering the traditional pathway FTCS pathway. The retention of the 11–13‐week NT ultrasound remains important in the detection of structural anomalies; however, the optimal management of pregnancies with a low‐risk NIPT result and an isolated increased NT measurement in an era of advanced genomic testing options is a new dilemma for clinicians. For parents, the prolonged period between the initial diagnosis in first trimester, and prognostic information at each successive stage of investigations up to 22–24 weeks, can be emotionally challenging. This article addresses the common questions from parents and clinicians as they navigate the uncertainty of having a fetus diagnosed with an increased NT after a low‐risk NIPT result and presents suggested approaches to management.

Many non-invasive prenatal testing (NIPT) platforms screen for sex chromosome aneuploidy (SCA) and SCA analysis is generally included in Australia where NIPT is available as a self-funded test. Little is known about the experience of receiving an NIPT result indicating an increased chance of SCA. This study aimed to explore the experi-

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