Trends in live birth prevalence of Down syndrome in the Northern Netherlands 1987-96: the impact of screening and prenatal diagnosis

In the Northern Netherlands, we examined the live birth prevalence of Down syndrome (DS) and the impact of maternal serum screening (MSS) and prenatal cytogenetic diagnosis (PCD) during the period 1987-96. In this period the live birth prevalence, based on the maternal age distribution and the age s pecific risk of delivering a child with DS was expected to increase from 1. 26 in 1987 to 1.62 in 1996. The introduction of MSS in 1991 made PCD availa ble to women of all ages. Nevertheless, the utilization of PCD remained ver y stable. In 1991, 4.7% of pregnant women underwent a diagnostic test. In 1 996 this percentage was 6.4%. As a result of MSS and PCD, the live birth pr evalence of DS was 19% lower than expected (p<0.01). Despite utilization of PCD based on opting-in and a discouraging government policy regarding the offer of MSS, the percentage of DS cases detected by PCD increased from of 17% during the period 1987-90 to 27% in the period 1991-96 when MSS was ava ilable. The percentages have been corrected for spontaneous pregnancy loss. From a medical and financial point of view, MSS was the most cost-effectiv e indication for PCD. However, the potential of reducing the birth prevalen ce of DS is limited by the low utilization of MSS and PCD by pregnant women . Copyright (C) 2000 John Wiley & Sons, Ltd.