Twenty-year trends in the prevalence of Down syndrome and other trisomies in Europe: impact of maternal age and prenatal screening

Abstract

This study examines trends and geographical differences in total and live birth prevalence of trisomies 21, 18 and 13 with regard to increasing maternal age and prenatal diagnosis in Europe. Twenty-one population-based EUROCAT registries covering 6.1 million births between 1990 and 2009 participated. Trisomy cases included live births, fetal deaths from 20 weeks gestational age and terminations of pregnancy for fetal anomaly. We present correction to 20 weeks gestational age (ie, correcting early terminations for the probability of fetal survival to 20 weeks) to allow for artefactual screening-related differences in total prevalence. Poisson regression was used. The proportion of births in the population to mothers aged 35+ years in the participating registries increased from 13% in 1990 to 19% in 2009. Total prevalence per 10000 births was 22.0 (95% CI 21.7-22.4) for trisomy 21, 5.0 (95% CI 4.8-5.1) for trisomy 18 and 2.0 (95% CI 1.9-2.2) for trisomy 13; live birth prevalence was 11.2 (95% CI 10.9-11.5) for trisomy 21, 1.04 (95% CI 0.96-1.12) for trisomy 18 and 0.48 (95% CI 0.43-0.54) for trisomy 13. There was an increase in total and total corrected prevalence of all three trisomies over time, mainly explained by increasing maternal age. Live birth prevalence remained stable over time. For trisomy 21, there was a three-fold variation in live birth prevalence between countries. The rise in maternal age has led to an increase in the number of trisomy-affected pregnancies in Europe. Live birth prevalence has remained stable overall. Differences in prenatal screening and termination between countries lead to wide variation in live birth prevalence.

Figure 1

Total corrected prevalence per 10 000 births (log scale) of trisomies 21, 18 and 13 by maternal age, 1990–2009, 12 European countries.

Figure 2

Total and LB prevalence per 10 000 births of trisomy 21, 18 and 13 in 12 European countries, 1990-2009.

Figure 3

LB and total corrected prevalence (with 95% CI) per 10 000 births of trisomy 21 in 2000–2009, 12 European countries (countries are ordered by % mothers 35+ years in 2000–2009). Total corrected=LB+FD+TOPFA corrected to 20 weeks GA.

Figure 4

Proportion (with 95%CI) of trisomy 21 cases prenatally diagnosed according to maternal age, 9 European countries.

Figure 5

Proportion of trisomy 21 cases prenatally diagnosed by type of prenatal test first indicating or leading to prenatal diagnosis, 9 European countries, 2005–2009. US, Ultrasound CVS/ amnio, Chorionic villus sampling or amniocentesis. *Ireland (Cork and Kerry, South East Ireland), UK (Northern England, Thames Valley, Wales, Wessex).