Screening for Down's syndrome: experience in an inner city health district

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Abstract
Objective To review the experience of Down's syndrome screening in an inner city health district.Design In this retrospective study the names of the women were obtained from the Regional Cytogenetic Laboratory and District Down's Syndrome Register. Antenatal notes of the mothers were studied. Maternal age during the affected pregnancy, screening test performed if any, gestational age at booking and at screening, screening test results, and pregnancy outcome were reviewed.Setting An inner city health district.Population Down's syndrome cases diagnosed prenatally and postnatally.Interventions None.Results Antenatal diagnosis of Down's syndrome was made in 15/45 women (33.3%); Edwards' syndrome was diagnosed antenatally in 2/5 women. Screening was not performed in eight women (17.8%) whose infants were affected by Down's Syndrome; it was also not performed in one woman whose baby was affected by Edwards' syndrome due to late presentation to the antenatal clinic or loss of the blood sample. Nineteen women (42.2%) with a Down's syndrome pregnancy and two women with a Edwards' syndrome pregnancy had had a negative screening test. Three women had had a positive screening test but declined amniocentesis. Among those who had a screening test, the overall detection rate of screening was 48.6% (18/37) for Down's syndrome and 50% (2/4) for Edwards' syndrome. The detection rates in different ethnic groups did not show significant difference. Four women chose not to have termination following diagnosis of Down's syndrome, giving a total reduction rate of 21 %.Conclusion Screening programmes for Down's syndrome have not yet resulted in a substantial reduction in the number of affected babies. In addition to trials at developing screening programmes with better detection rates, efforts should be made to improve the provision of the screening service and the quality of antenatal care in general with emphasis on early presentation and optimal understanding of the implications of the tests.