Prevalence of Down syndrome in Glasgow, 1980-96--the growing impact of prenatal diagnosis on younger mothers.
OBJECTIVE
To assess the impact of improved methods of prenatal diagnosis on the prevalence of Down Syndrome (DS).


METHODS
Registry based epidemiological study.


METHODS
Glasgow Register of Congenital Anomalies, Greater Glasgow Health Board, Scotland.


METHODS
All registered cases of DS diagnosed at or after birth plus terminations following prenatal diagnosis from 1980 to 1996. Denominator data (total births to mothers resident in GGHB) were obtained from the Registrar General for Scotland.


RESULTS
A total of 293 cases of DS were registered over the 17 year period. Of these, 198 (68%) were live births, 8 (3%) stillbirths and 84 (29%) induced abortions following prenatal diagnosis. There were 212,724 total births to women in the GGHB area over the same period, giving a period pregnancy prevalence of 1.36 per 1000 total births (95% CI 1.21-1.53). After correcting for spontaneous losses, the adjusted pregnancy prevalence was 1.24 per 1000 total births. The pregnancy prevalence of DS rose over time. One hundred and two (35%) of cases of DS were diagnosed prenatally. The annual proportion of DS cases diagnosed prenatally slowly increased to around 60% towards the end of the period. The termination rate also increased, especially in younger (under35) women. A change in this rate in 1987 coincided with the introduction of the triple test.


CONCLUSIONS
The epidemiological impact of antenatal screening and subsequent prenatal diagnosis is clear with pregnancy and birth prevalence rates diverging steadily over time since the late 1980s. The rising termination rate in younger women suggests that the benefits of antenatal screening are now extending to the lower risk younger age groups.
Iliyasu
Z
Z
Department of Public Health, University of Glasgow, Glasgow.
Gilmour
W H
WH
Stone
D H
DH
D000328:Adult; D016009:Chi-Square Distribution; D004314:Down Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011296:Prenatal Diagnosis; D015995:Prevalence; D012042:Registries; D012606:Scotland / Q000453:epidemiology