POPULATION SCREENING FOR ANEUPLOIDY USING MATERNAL AGE AND ULTRASOUND

The coexistence of an epidemiological register and a multidisciplinary centre for prenatal diagnosis prompted us to report data collected du ring six years (1990-1995) in Isere county on prenatally detected chro mosomal aberrations. During the whole study period prenatal diagnosis strategy towards chromosome aberrations was based solely on maternal a ge and ultrasound examination. Results showed a respective contributio n of one-third/two-thirds for the two detection modes (maternal age/ul trasound signs). From 1990 to 1995 a significant increase in the propo rtion of prenatally detected autosomal aneuploidy was observed, from 5 2 per cent to 75 per cent (P<0.001). This significant variation was ma inly due to an increase in the proportion of prenatally detected triso my 21 cases, and to an increase in the proportion of aberrations which were detected through first trimester ultrasound examination. The hig hest positive predictive values were observed for polymalformation, ca rdiac anomalies and cystic hygroma ultrasound signs (51 per cent, 21 p er cent and 26 per cent; respectively). Our results for trisomy 21 are close to those obtained in other studies, even when prenatal strategi es are different. Their interest lies in the fact that they can be con sidered as a reference level of prenatal diagnosis efficiency due to a strategy based on maternal age and ultrasound signs, a level which ha s to be taken into account when evaluating the benefits of additional serum screening policies in other studies. (C) 1998 John Wiley & Sons, Ltd.