Antenatal findings and early postnatal outcomes in pregnancies with trisomy 21: a 10 year retrospective review at a tertiary centre.

OBJECTIVE: To examine the antenatal imaging features, intrapartum findings and early postpartum course of pregnancies with trisomy 21 (T21) at a tertiary hospital in the United Kingdom. METHODS: Women with pregnancies diagnosed with T21 on antenatal or post-mortem/postnatal karyotyping, from February 2010-2020. Outcome measures included antenatal imaging findings, fetal growth restriction (FGR), birthweight, mode of delivery and early neonatal outcomes. RESULTS: 76 women were included. There were six intrauterine deaths and 70 livebirths. Thirty-eight (50%) had an antenatal diagnosis and twenty-five (33%) had a suspected diagnosis but declined further testing. The diagnosis was unanticipated in 13 (17%). Cardiac anomalies (35.5%) were the most common antenatal anomaly. Doppler abnormalities were apparent in 48/73 (68%). Eighteen (25.7%) had antenatal FGR. The majority were delivered by Caesarean section, and 21.4% of babies weighed

Cytogenomic results following high-chance non-invasive prenatal testing: a UK national audit.

OBJECTIVE: Non-invasive prenatal testing (NIPT) is increasingly being adopted as a screening test in the UK and is currently accessed through certain National Health Service healthcare systems or by private provision. This audit aims to describe reasons for and results of cytogenomic investigations carried out within UK genetic laboratories following an NIPT result indicating increased chance of cytogenomic abnormality ('high-chance NIPT result'). METHOD: A questionnaire was sent out to 24 genetics laboratories in the UK and completed by 18/24 (75%). RESULTS: Data were returned representing 1831 singleton pregnancies. A total of 1329 (73%) invasive samples were taken following NIPT results showing a high chance of trisomy 21; this was confirmed in 1305 (98%) of these by invasive sampling. Trisomy 21 was confirmed in >99% of patients who also had high-screen risk results or abnormal scan findings. Amongst invasive samples taken due to NIPT results indicating a high chance of trisomy 18, 84% yielded a compatible result, and this number dropped to 49% for trisomy 13 and 51% for sex chromosomes. CONCLUSION: In the UK, the majority of patients having invasive sampling for high-chance NIPT results are doing so following an NIPT result indicating an increased chance of common trisomies (92%). In this population, NIPT performs particularly well for trisomy 21, but less well for other indications.

Incidence of placental mosaicism leading to discrepant results between QF-PCR and karyotyping in 22,825 chorionic villus samples.

OBJECTIVE: To review the frequency and analyse the origin of completely discrepant results observed between QF-PCR and karyotyping in chorionic villus samples (CVS) as a result of placental mosaicism. Also, to assess QF-PCR results for biallelic or triallelic patterns and determine their significance. METHODS: Between May 2002 and December 2009, 22 825 CVS were received at TDL Genetics for processing by QF-PCR and karyotype. The QF-PCR and karyotype data were compared to determine the incidence of discrepant results. RESULTS: Of the 22 825 samples received, 22 779 (99.8%) gave concordant results between the PCR and karyotype, and 46 samples (0.2%) gave discordant results. Of these discrepant cases, 5 displayed triallelic peaks and 41 displayed biallelic peaks. All discordant results are due to the presence of placental mosaicism, a known limitation of using this sample type for prenatal diagnosis. CONCLUSION: This retrospective study of placental mosaicism in CVS is the largest single centre study to date and provides a figure for the occurrence of completely discrepant results between QF-PCR and karyotype due to placental mosaicism. This study also demonstrates that the presence of triallelic peaks at QF-PCR is not sufficient to exclude the presence of placental mosaicism.

A novel method for extracting DNA from chorionic villus samples for use in CVS-PCR, which ensures complete villus dissociation.

OBJECTIVE: To demonstrate that glass disruption beads dissociate chorionic villus samples releasing DNA from mesenchymal and cytotrophoblast cells that is suitable for processing by CVS-PCR (rapid molecular aneuploidy testing). This method is quicker than conventional methods and may limit discrepancies between PCR and karyotype in certain types of placental mosaicism. METHOD: DNA was extracted from villus samples by mechanical disruption of the cells using glass beads. This method was compared to collagenase incubation followed by chelex extraction of the digested villus. PCR data generated were compared using standard criteria. RESULTS: DNA extracted by glass bead disruption generated data of equivalent quality to that obtained from DNA extracted using conventional collagenase and chelex-based extraction method. The case study demonstrates probable cytotrophoblast enrichment of a sample when processed by collagenase digestion and chelex incubation. Re-extraction of the digested sample by glass bead disruption resulted in cytotrophoblast and mesenchyme cells contributing to the supernatant. CONCLUSION: Glass bead disruption of chorionic villus samples is an effective, inexpensive and rapid DNA extraction method that dissociates villus ensuring that DNA from both cytotrophoblast and mesenchyme cells is represented in the supernatant. Extracted DNA produced is suitable for CVS-PCR and can be stored stably at - 20 degrees C.