Key points are not available for this paper at this time.
Outcome of antenatal Down's syndrome screening.Values are numbers (percentages; 95% confidence intervals) unless otherwise indicated All women White and other Indian Asians Total eligible for screening 9217 7562 1655 Uptake of serum screening 7953 (86.3) 6765 (89-5) 1188 (71-8) Women screened positive 382 (4-8) 236 (3-5) 146 (12-3) Relative risk 3.5 (2-9 to 4-3) Amniocentesis uptake 179 (48) 142 (60) 37 (27) X12 43-9 (P<0.001)Detection rate for Down's syndrome 5/14 (36) 5/12 0/2 (42; 13 to 72) (0; to 84) Positive predictive value 1:76 (5/382) 1:47 0:146 No of cases of Down's syndrome: Identified antenatally 6* 6* 0 Identified postnatally 12t 9t 3t Rate per 1000 births 1.8* 1.8* 1.8 *Includes one case of Down's syndrome identified by primary amniocentesis; details available from the authors on request.tlncludes the Down's syndrome births missed by serum screening and those occurring in unscreened women.*After a 23% reduction in antenatally diagnosed and terminated cases to allow for the increased fetal death rate in pregnancies with Down's syndrome diagnosed by amniocentesis but not ending in a termination.'
Thompson et al. (1996) studied this question.