Prevalence of Down's syndrome in a pregnant population in Finland


Markku Ryynanen, Department of Obstetrics and Gynecology, Oulu University Hospital, PL 24, 90020 OYS, Finland. E-mail:


The characteristics of the Finnish parturient have changed in recent years. The mean age of mothers at first delivery is now 29.3 years and the number of women > 35 years of age has increased to 19%. This shift has led to an increase in the prevalence of Down's syndrome. Between 1 January 2002 and 31 December 2006, there were 795 cases of Down's syndrome (27/10,000) in the Finnish Register of Congenital Malformations. The distribution of Down's syndrome in terminated pregnancies and newborns was analyzed in 5-year periods based on maternal age. The distribution of Down's syndrome cases in younger women (< 35 years) and in older women (≥35 years) at the time of delivery was compared. The majority of new Down's syndrome cases occurred in the group having older women (61.1%), even though 35 years is the arbitrary threshold.