[Prenatal diagnosis and prevalence of Down syndrome in the Parisian population, 2001-2005].

OBJECTIVES To assess recent trends in the prevalence of Down syndrome and the proportion of cases with a prenatal diagnosis in the Parisian population. PATIENTS AND METHODS Four hundred and ninety-nine cases of Down syndrome were registered by the Paris Registry of Congenital Anomalies during the period 2001-2005. All cases with prenatal diagnosis were confirmed by cytogenetic examination. We analyzed trends in the total and live birth prevalence, the proportion of cases with a prenatal diagnosis and those with a pregnancy termination, as well as gestational age at diagnosis and termination. Analyses were stratified by maternal age and trends were tested by the Cochran-Armitage test and Anova. RESULTS Total prevalence of Down syndrome remained high (37.6 per 10,000 births, 95%CI 34.2-40.9) during this period because of advanced maternal age in Paris. The proportion of cases with a prenatal diagnosis (overall average 85.5%, 95% CI 81.8-88.1), and live birth prevalence of Down syndrome (7.1 per 10,000 live births, 95%CI 5.7-8.6) have remained fairly stable over time. The great majority of women (95% CI 95% 92.7-96.9) opted for a pregnancy termination following a prenatal diagnosis of Down syndrome. A trend towards an earlier gestational age at prenatal diagnosis was noted among women less than 30 years of age. DISCUSSION AND CONCLUSION It is important to continue to evaluate changes in the prenatal diagnosis of Down syndrome, notably in view of potential changes in screening practices and policies, and particularly if a first trimester strategy is adopted following recent recommendation by the "Haute Autorité de santé".