Collaborative study of maternal urine beta-core human chorionic gonadotrophin screening for Down syndrome

Several studies have shown that second-trimester maternal urine beta-core h uman chorionic gonadotrophin (hCG) levels are raised on average in Down syn drome pregnancies. However, in all but one, testing was retrospective after extended sample storage and so we carried out a large international multic entre prospective study. 16 centres provided 6730 samples from 14-19 week p regnancies: 39 with Down syndrome, 12 with Edwards' syndrome, 42 with other aneuploidies, 52 unaffected twins and 6585 singleton unaffected pregnancie s. Samples were from those having routine maternal serum screening in 6 cen tres and invasive prenatal diagnosis for reasons unrelated to maternal seru m screening in 10 centres. Normalized levels of beta-core hCG (nmom/mmol cr eatinine) were expressed as multiples of the gestation-specific normal medi an (MoMs). The median beta-core hCG level in Down syndrome was 1.70 MoM (95 per cent confidence interval, 1.26-2.30); 14 (36 per cent) exceeded the no rmal 90th centile and 9 (23 per cent) the 95th centile. The median level in Edwards' syndrome was 0.23 MoM. On the basis of our results alone it is unlikely that urinary beta-core hCG will be a useful marker in Down syndrome screening practice. But the consi derable variability in results between studies means that further research is needed before a reliable conclusion can be drawn. Copyright (C) 1999 Joh n Wiley & Sons, Ltd.