The trends in maternal age distribution and the estimated live birth and population prevalence of Down syndrome in China: 1985-2012

This study aims to investigate the trends in maternal age distribution and estimate the live birth and population prevalence of Downs syndrome in China. Using population survey data, we demonstrated the change of maternal age over the past three decades and its effect on the live birth prevalence of Downs syndrome. We also integrated the live birth prevalence and the survival rate to estimate the population prevalence of Downs syndrome. Chi-square test was used to compare the maternal age distributions across survey years. The results show that the maternal age has been rising over the past 30 years in China at national level. The proportion of mothers aged 35 and over increased from 3.62% in 1985 to 14.40% in 2010. The estimated live birth prevalence of Downs syndrome has mirrored the same increase of the maternal age from 1.07 per 1000 live births in 1985 to 2.36 per 1000 live births in 2010. At City level, the change of maternal age and live birth prevalence of Downs syndrome were more significant than at Town and County levels. The proportion of mothers aged 35 and over increased from 2.17% in 1995 to about 16% in 2010 at City level, while it increased from 2.03% to 13.65% at County level. The total estimated number of people with Downs syndrome who were still alive in 2012 and aged below 27 was 611,053, and the estimated population prevalence is 0.45 per 1000. To conclude, this study provides a clear message about the rising trend in maternal age in both urban and rural areas in China since 1985 and its effect on the estimated birth prevalence with Downs syndrome. The regional differences should be taken into account for planning population policy and allocating medical resources to reduce the burden of family with Downs syndrome.