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.
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.


METHODS
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.


CONCLUSIONS
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.
Muller
Peter R
PR
Department of Perinatal Medicine, Women's and Children's Hospital, North Adelaide, South Australia, Australia 5006. mullerp@wch.sa.gov.au
Cocciolone
Robert
R
Haan
Eric A
EA
Wilkinson
Chris
C
Scott
Heather
H
Sage
Leonie
L
Bird
Renata
R
Hutchinson
Rhonda
R
Chan
Annabelle
A
D000328:Adult; D016009:Chi-Square Distribution; D015331:Cohort Studies; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008403:Mass Screening / Q000458:organization & administration*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D011336:Probability; D016730:Program Development; D015397:Program Evaluation; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013021:South Australia