Trends in state/population-based Down syndrome screening and invasive prenatal testing with the introduction of first-trimester combined Down syndrome screening, South Australia, 1995-2005

Abstract

Objective The purpose of this study was to review trends in the us of maternal serum Down syndrome screening and invasive prenatal testing before and after the introduction of a state-based first-trimester combined Down syndrome screening program. Study Design A retrospective population-based study was performed on first- and second-trimester Down syndrome screening, invasive prenatal testing, and prenatal detection of Down syndrome from 1995 to 2005 in South Australia with data from state-based registers. Chi-square tests were used to evaluate trends. Results There was a significant decrease in the use of second-trimester Down syndrome maternal serum screening (from 75% in 1995 to 25% in 2005; P < .001) and a corresponding significant increase in first-trimester combined screening (from 0.8% in 2000 to 49% in 2005; P < .001). The proportion of all confinements that involved invasive prenatal testing fell (from 9.3% in 1995 to 7.6% in 2005; P < .001). There was a significant decrease in the number of invasive prenatal tests that were needed to detect 1 Down syndrome fetus (from 86 tests in 1995 to 40 tests in 2005; P < .001), with no significant change in the proportion of Down syndrome cases that were detected prenatally. Conclusion The introduction and increased use of first-trimester combined Down syndrome screening has been associated with more efficient use of invasive prenatal testing in South Australia and has maintained a high level of overall prenatal detection.