Increasing maternal age is not a significant cause of false-positive results for monosomy X in non-invasive prenatal testing.

OBJECTIVE: The accuracy of cell-free DNA aneuploidy screening varies by the chromosome assessed. The positive predictive value is consistently low for monosomy X (MX), at less than 30%. This study aims to investigate maternal age and other possible predictors of false-positive MX screening results in order to guide pre-test and post-test counselling. METHODS: A total of 52 499 NIPT samples were tested over 69 months, across three specialist obstetric services. Outcome data were available for 96 out of 107 cases high risk for MX. Cytogenetic outcomes were compared to clinical and demographic data to look for trends that may indicate higher likelihood of a false-positive NIPT result. RESULTS: The likelihood of a false-positive MX result significantly increased with the absence of ultrasound features suggestive of MX and with lower PAPP-A levels. Non-significant trends towards false-positive results were identified with increased maternal age, increased body mass index and Caucasian ethnicity. CONCLUSION: Maternal age is not a reliable predictor of a false-positive result. Assessment of ultrasound findings and placental serology in the first trimester is important for appropriate post-test counselling and should continue to be a part of screening even when NIPT is used as a first-tier screening test.

Parental experiences and genetic counsellor roles in Pierre Robin sequence.

Pierre Robin sequence (PRS) is a craniofacial abnormality comprising micrognathia, glossoptosis and airway obstruction, which can impair the newborn's feeding and breathing. While there has been much research around the cause of PRS and most appropriate methods of care, understanding the psychosocial aspects of a PRS diagnosis from the parents' perspective is lacking. The aim of this study is to understand parental experiences of having a child diagnosed with PRS, as well as the role of genetic counselling in PRS. Fourteen semi-structured interviews were conducted with parents of children diagnosed with isolated PRS between 2 and 5 years prior. From these 14 interviews, eleven transcripts were analysed to find common themes and experiences. The diagnosis was confusing and overwhelming for participants during emotionally sensitive periods and little was understood about the cause of their child's PRS. Those participants who did recall experiences with genetic services reported that they were minimal and uninformative. According to participant recollection, genetic counselling was rarely offered, despite there being a potential for this service in PRS. Genetic counselling would be a valuable source of information and support for parents both at the time of antenatal diagnosis, and potentially 6 to 12 months later in the outpatient environment when these children are all routinely reviewed by their clinical care team.

Rare autosomal trisomies: Important and not so rare.

OBJECTIVE: Noninvasive prenatal testing (NIPT) can assess chromosomes other than 13, 18, 21, X and Y. These rare autosomal trisomies (RATs) can adversely affect pregnancy outcome. METHODS: A prospective study of NIPT using the Illumina sequencing platform assessing all chromosomes were reported for further management. RESULTS: There were 28 RATs identified in 23 388 samples (one in 835), the most common being trisomy 7 (n = 6), followed by trisomy 16 (n = 4) and trisomy 22 (n = 3). Abnormal outcomes occurred in 16 cases: miscarriage (n = 6), true fetal mosaicism (n = 5), and fetal structural anomaly on ultrasound (n = 5). Growth restriction was seen in eight cases and correlated with very low-pregnancy-associated plasma protein-A levels. Two of the 17 live born babies had a structural anomaly, and one had a phenotype similar to mosaic trisomy 16 despite a normal microarray result. CONCLUSION: Rare autosomal trisomies are not rare and often associated with poor obstetric outcomes. They should be discussed with the clinician to guide management. Pregnancy outcomes varied by chromosome being generally favourable for some (eg, trisomy 7) and poor for others (eg, trisomy 22). In the presence of a RAT, pregnancy-associated plasma protein-A is predictive of placental dysfunction and fetal growth restriction.