Serum screening for Down syndrome and adverse pregnancy outcomes: a case-controlled study.

The relationship between adverse perinatal outcomes in women with false positive biochemical screening test for Down syndrome was investigated in a retrospective case-controlled study. A cohort of 4000 women who booked for routine antenatal care and opted for biochemical screening over a 22 month period was obtained. The pregnancy outcome data of 272 women with a false positive screening test for Down syndrome (risk >1 in 250) at 15-18 weeks of gestation (study group) were compared with data from 272 age and gestation matched controls with a negative Down syndrome screening test from the same population. The frequency of normal and adverse perinatal outcomes, including pre-eclampsia, isolated intrauterine growth restriction, spontaneous preterm labour and stillbirth was recorded. The incidence of adverse pregnancy outcomes was 11.9% in the study group and 8.6% in the control group. The estimated odds ratio of an abnormal outcome in the study group was 1.41 (95% CI-0.790, 2.55). The observed difference between proportion was 0.0324 (95% CI-0.022, 0.083; p=0.40). These data identify no evidence for a strong association between a false positive Down syndrome screening test result and subsequent adverse perinatal outcomes in the general population.