Abnormalities of sex chromosomes are identified in approximately 1% of all pregnancies that undergo a prenatal karyotype. There is a need to review the prenatal as well as postnatal care of the affected mother and offspring.

Introduction Prenatal diagnosis (PND) via amniocentesis or chorionic villus sampling may result in the identification of a sex chromosome abnormality, often as an incidental finding. Aims To ascertain the incidence of sex chromosome abnormalities detected by prenatal diagnosis in the Grampian and the West of Scotland (WoS) regions and to determine the characteristics and outcomes of these cases. Methods Retrospective review of all cases of prenatal diagnoses that revealed a sex chromosome abnormality between 2000 and 2012. Results Over the period of 12 years, 166 positive cases were identified. The indication for PND was an abnormal ultrasound scan in 95(57%), high-risk first trimester screening results in 31(19%), age related aneuploidy risk in 24(14%), maternal anxiety in 9(5%) and a family history of a chromosomal abnormality in 7(4%). Of the 166 cases, 79(48%) cases were 45, X, 24(14%) were 47, XXY, 14(8%) were 48, XXX, 9(5%) were 45, X/46, XX,, 8(5%) had a structurally abnormal X chromosome, 7(4%) were 45X/46XY, 6(4%) were 48, XYY, 2(1%) were 46, XX/46XY and 17(11%) had other variations of sex chromosomes. Of the 166, 73(44%) pregnancies were terminated and of these cases, 47(64%) had a karyotype of 45, X. An additional 7 pregnancies(4%) were associated with an intrauterine death and 5 of these were 45, X. Based on a combined birth rate of 40,000 births per year for these regions, it is estimated that there was one positive case for 3,500 births and approximately half of these led to a live birth. Conclusions 1:7000 births are associated with a prenatally diagnosed sex chromosome abnormality. 45, X is the most commonly encountered abnormality. Given the rare incidence, there is a need to improve our understanding of the care of these cases during the pregnancy as well as afterwards.

Current health policy encourages the use of rapid trisomy testing rather than full karyotype analysis. We compared the results of QF-PCR with full karyotyping via a retrospective audit. Between 01/11/09 and 31/10/11, 1726 CVS or amniocentesis samples from prenatal diagnostic procedures were received in the regional genetics laboratory which serves a population of 3 million. Main referral reason was due to abnormal scan (52%), followed by increased risk at second trimester screening (31%). Family history of chromosomal anomalies (7%) and maternal age (5%) were less common indications. Three cases had inadequate sample for culture, 1 failed culture and 1 was not set up. Abnormal karyotype was seen in 181 samples: 71% of abnormalities were correctly identifi ed at the time of QF-PCR. Approximately 50% had trisomy 21, 25% had trisomy 18 and the remainder had Turner's syndrome, 69 XXX, or trisomy 13. In 51 cases, QF-PCR did not detect the abnormality seen at full karyotyping. Of these, 16 cases had balanced translocation or inversion and 15 had normal ultrasound examinations. Thirteen had unbalanced changes and 10 of these also had abnormal scans. Due to referral reasons (e.g. maternal age or biochemical screening), sex chromosomes were not always examined at QF-PCR. Fourteen cases of XO / XXX / XXY were missed. There were 4 samples with mosaicism but only 1 case also had an abnormal scan. Valuable additional information can be obtained by full karyotyping. However, in those with severe chromosomal abnormalities, structural anomalies are often seen on ultrasound examination.group.bmj.com on June 9, 2015 -Published by http://fn.bmj.com/ Downloaded from

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