An assessment of the Down syndrome antenatal screening policies of East and West Gloucestershire between 1993 and 1999

Abstract

This retrospective observational study of registered pregnancies in Gloucestershire between 1 April 1993 and 31 March 1999 compares the impact of different Down syndrome antenatal screening policies on detection and amniocentesis rates. The screening policies in East and West Gloucestershire are based on early second-trimester maternal serum and maternal age screening, respectively. Maternal serum screening can identify a greater proportion of pregnancies affected by Down syndrome than a programme founded on age-based amniocentesis and 20 weeks' ultrasound. In addition, maternal serum screening of women older than 34 approximately halves the number of amniocenteses performed to detect one affected fetus. However, the proportion of pregnant women who have amniocentesis is nearly doubled by offering serum screening to women aged over 24 years. These findings of the impact of established second-trimester screening policies in low-risk populations provides an useful benchmark to compare the performance of screening procedures that will be introduced in the United Kingdom over the next 3 years.