Sex chromosome trisomies in Europe: prevalence, prenatal detection and outcome of pregnancy

Abstract

This study aims to assess prevalence and pregnancy outcome for sex chromosome trisomies (SCTs) diagnosed prenatally or in the first year of life. Data held by the European Surveillance of Congenital Anomalies (EUROCAT) database on SCT cases delivered 2000-2005 from 19 population-based registries in 11 European countries covering 2.5 million births were analysed. Cases included were livebirths diagnosed to 1 year of age, fetal deaths from 20 weeks gestation and terminations of pregnancy for fetal anomaly (TOPFA). In all, 465 cases of SCT were diagnosed between 2000 and 2005, a prevalence of 1.88 per 10,000 births (95% CI 1.71-2.06). Prevalence of XXX, XXY and XYY were 0.54 (95% CI 0.46-0.64), 1.04 (95% CI 0.92-1.17) and 0.30 (95% CI 0.24-0.38), respectively. In all, 415 (89%) were prenatally diagnosed and 151 (36%) of these resulted in TOPFA. There was wide country variation in prevalence (0.19-5.36 per 1000), proportion prenatally diagnosed (50-100%) and proportion of prenatally diagnosed resulting in TOPFA (13-67%). Prevalence of prenatally diagnosed cases was higher in countries with high prenatal detection rates of Down syndrome. The EUROCAT prevalence rate for SCTs diagnosed prenatally or up to 1 year of age represents 12% of the prevalence expected from cytogenetic studies of newborn babies, as the majority of cases are never diagnosed or are diagnosed later in life. There is a wide variation between European countries in prevalence, prenatal detection and TOPFA proportions, related to differences in screening policies as well as organizational and cultural factors.

Figure 1

Observed and expected prevalence per 10 000 births for sex chromosome trisomies, 2000–2005.

Figure 2

Percentage of sex trisomy cases prenatally diagnosed and the percentage of prenatally diagnosed cases resulting in termination of pregnancy for fetal anomaly, for each sex chromosome anomaly. PD, prenatal diagnosis.

Figure 3

Relationship between prevalence of prenatally diagnosed sex chromosome trisomies and proportion of Down's syndrome cases detected prenatally. The percentages below are the percentage of Down's syndrome cases prenatally diagnosed and the prevalences cited are the prevalence of prenatally diagnosed sex chromosome trisomies per 10 000 births. Mothers <35 years: Austria 54%, 0.37; Belgium 52%, 0.53; Denmark 38%, 0.00; France 80%, 1.03; Germany 60%, 0.74; Italy 56%, 0.98; Poland 4%, 0.00; Spain 67%, 1.38; Switzerland 88%, 1.78; UK 48%, 0.33. Mothers 35+ years: Austria 73%, 6.79; Belgium 66%, 5.86; Denmark 87%, 6.05; France 94%, 8.84; Germany 83%, 6.07; Italy 85%, 7.04; Poland 4%, 1.14; Spain 88%, 5.57; Switzerland 94%, 17.67; UK 70%, 4.15. Analysis based on 17 out of 19 registries—Hainaut (Belgium) and South Portugal were excluded as maternal age denominators available for <80% of the population.