Current French practices for prenatal diagnosis of trisomy 21: a population-based study in Paris, 1992-97

The results and limitations of current French practices for prenatal diagno sis (PND) of trisomy 21 were examined, using population-based data from the Paris Registry for 1992-97 (219 000 births). Of 670 cases of trisomy 21 re ported, 71.0 per cent were terminations of pregnancy (TOP). The PND rate am ong mothers 38 years and older, all of whom were offered amniocentesis, was 89.9 per cent. Nearly all affected births in this age class followed mater nal decisions, either to refuse amniocentesis or continue the affected preg nancy. In younger mothers, the overall French prenatal screening policy (th ree ultrasound examinations plus serum screening from January 1997) led to an overall PND rate of 67.3 per cent; it reached 78.8 per cent in 1997. Ult rasound accounted for 73.4 per cent of diagnosed cases, Increased detection by nuchal translucency measurement is clearly visible from 1996 onward. Th e birth prevalence, 8.7 per 10 000 births, diminished only slightly over th e study period. The increase observed in the total number of cases in 1996 and 1997, concomitant with PND practice trends, may be due primarily to ear lier TOP, which precedes miscarriages that would otherwise have occurred wi thout being recorded. Future trends in prevalence among births must be obse rved carefully. Copyright 1999 John Wiley & Sons, Ltd.