Vaginal bleeding in pregnancies associated with fetal Down syndrome

It has been suggested that vaginal bleeding in pregnancy is associated with an increased risk of fetal Down syndrome. To investigate this, information on vaginal bleeding, collected at the first antenatal visit, was abstracted from the medical notes of 70 pregnancies associated with Down syndrome and 140 unaffected controls matched for maternal age. Fourteen cases (20 per cent) and 23 controls (16 per cent) had some evidence of bleeding (relative risk estimated as the odds ratio = 1.3; P = 0.26, one-sided; 95 per cent confidence interval 0.6-2.8). When these results were pooled with those from the two other controlled studies already published the combined relative risk estimate was 1.8 (P = 0.02, two-sided; 95 per cent confidence interval 1.1-3.0). On the basis of present evidence, there is some reason to regard vaginal bleeding prior to the first antenatal visit as a risk factor for Down syndrome but the association and its biological significance remains uncertain.