SP1 in pregnancies with Down syndrome in the first trimester of pregnancy

We conducted a study to determine the value of serum pregnancy-specific bet a-1-glycoprotein (Schwanger-schafts protein 1, SP1) as an antenatal screeni ng test for Down syndrome in the first trimester. Serum samples collected f rom women at 8 to 14 weeks of pregnancy, immediately prior to having a chor ionic virus sampling procedure on account of advanced maternal age, were re trieved from 96 women with Down syndrome pregnancies (cases) and from 480 w omen with unaffected pregnancies (controls). Cases and controls were ascert ained at 21 obstetric centres in nine countries. Each case was matched with five controls for maternal age (same five-year age groups), duration of st orage of the serum sample (same calendar year) and gestational age (usually the same week of pregnancy). The levels of SP1 were lower in pregnancies a ssociated with Down syndrome: the median level was 0.86 multiples of the me dian level in the controls (95 per cent confidence interval 0.76 to 0.97). This difference, though statistically significant, was not large enough for SP1 to be a useful marker in screening, at least from 10 weeks onwards whe re most of our data lie. Copyright (C) 1999 John Wiley & Sons, Ltd.