Improved prenatal detection of chromosomal anomalies.

Abstract

Introduction: Prenatal screening for karyotype anomalies takes place in most European countries. In Denmark, the screening method was changed in 2005. The aim of this study was to study the trends in prevalence and prenatal detection rates of chromosome anomalies and Down syndrome (DS) over a 22-year period.

Material and methods: The study was based on data collected from the EUROCAT registry of congenital anomalies for Funen County. The registry includes information about live births, foetal deaths with a gestational age > 20 weeks and terminations of pregnancy after prenatal diagnosis of foetal anomaly (TOPFA). The study includes all foetuses/infants diagnosed with a chromosome anomaly born between 1986 and 2007 of a mother residing in Funen County.

Results: A total of 431 foetuses/infants had a chromosome anomaly corresponding to an overall prevalence of 35.6 chromosome anomalies per 10,000 births. This figure remained constant during the study period. Two hundred and three cases were live births (47% of total), 26 foetal deaths (6%) and 202 TOPFAs (47%). The prenatal detection rate for chromosome anomalies increased from 27% in the 1980s to 71% in the new millennium (p < 0.001). There were 235 cases with DS (55% of total cases), which yields an overall prevalence of 19 DS cases per 10,000 births.

Conclusion: The prevalence of all chromosomal anomalies and DS did not change over time. The prenatal DS detection rate more than doubled from 1986-1989 to 2000-2007. The number of TOPFAs increased, which is consistent with a decrease in the number of live births with DS as well as in all chromosomal anomalies.

Funding: not relevant.

Trial registration: not relevant.