Impact of maternal age distribution on the expected live birth prevalence of Down's syndrome in the metropolitan France between 1965 and 2008

Objectives. - To evaluate the impact of demographic factors such as maternal age on the expected prevalence of Down's syndrome at birth. Patients and methods. - We used data from the French National Institute of Statistics (INSEE) concerning live births and maternal age. Expected prevalence at birth is derived from a mathematical regression model commonly used in biochemical screening. Results. - We present continuous expected prevalence at birth over a long period, from 1965 to 2008. Over the last three decades, mean maternal age has increased by 4 years, leading to a two-fold increased in the expected live-birth prevalence of Down's syndrome infants, from 12.1 per 10,000 in 1977 to 21.7 per 10,000 in 2008. Conclusion. - It is important to continue to consider the impact modifications in demographic factors, such as maternal age, particularly in the evaluation of screening practices and policies for Down's syndrome. (C) 2010 Elsevier Masson SAS. All rights reserved.