Fetal loss in Down syndrome pregnancies.

It is recognized that pregnancies with Down syndrome are liable to end in spontaneous fetal loss. It is important to determine the magnitude of this effect so that it can be taken into account when assessing the results of antenatal screening programmes for Down syndrome. Failure to do so will tend to overestimate the detection rate in intervention studies in which the screening results are used to identify women for a diagnostic test and the offer of a termination of pregnancy if indicated. We present new data on the spontaneous fetal loss in Down syndrome pregnancies from the National Down Syndrome Cytogenetic Register (1989-1996). We compare our results with published results of other studies on the subject to obtain a summary estimate. We exclude one study from the meta analysis due to incorrect methodology resulting in an overestimate of fetal loss. Based on the combined data (i) between the time of chorionic villus sampling and term an estimated 43 per cent (95 per cent CI: 31-54 per cent) of pregnancies ended in a miscarriage or still birth, (ii) between the time of amniocentesis and term an estimated 23 per cent (95 per cent CI: 19 28 per cent) of pregnancies ended in a miscarriage or still birth, and (iii) 12 per cent (95 per cent CI: 2-23 per cent) of births were stillborn or resulted in a neonatal death.