[Prenatal diagnosis of Down syndrome in Denmark 1980-1998 and future progress perspectives]

The aim of the study was to describe maternal age-based screening for Down's syndrome (DS) in Denmark, 1980-1998, and to describe and discuss the possibilities for more effective screening procedures.

The prenatally diagnosed and delivered infants with DS as registered in the Danish Cytogenetic Registry, were compared with the expected number calculated from each year's maternal age distribution and the age-dependent DS incidence, taking into account the high probability of miscarriage in DS pregnancies. The expected performance of various screening procedures was calculated by Monte Carlo simulation.

Because of an older maternal age in the pregnant population, the annual expected number of infants with DS rose from about 60 in 1980 to about 110 in 1998. Despite a high frequency (about 11%) of invasive diagnostic procedures, the annual number of DS births also increased in the same period, namely from about 45 to about 65. It is calculated that a change from age-based screening to screening based on a serological risk evaluation could--with the full participation of all pregnant women--have reduced the total number of DS births in this period by about 300.

Revised guidelines from age-based screening to serological screening may potentially reduce the number of DS births cases in Denmark from about 65 per year to about 15.