G93 The Outcome Of Prenatal Identification Of A Sex Chromosome Abnormality

Abstract

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.