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To estimate the association between subchorionic hematoma and adverse perinatal outcomes.MEDLINE, EMBASE, and the Cochrane Library.We searched English language publications from January 1981 to August 2010 for cohort and case-control studies evaluating subchorionic hematoma and perinatal outcomes. The primary outcome was pregnancy loss (spontaneous abortion and stillbirth). Secondary outcomes were abruption, preterm premature rupture of membranes, preterm delivery, pre-eclampsia, and small for gestational age. Pooled odds ratios (ORs) were calculated from random effects models.Seven studies including 1,735 women with subchorionic hematoma and 70,703 controls met inclusion criteria. Subchorionic hematoma was associated with an increased risk of spontaneous abortion (from 8.9% to 17.6%; pooled OR 2.18, 95% confidence interval [CI] 1.29–3.68) and stillbirth (from 0.9% to 1.9%, pooled OR 2.09, 95% CI 1.20–3.67). The number needed to harm was 11 for spontaneous abortion and 103 for stillbirth, meaning one extra spontaneous abortion is estimated to occur for every 11 women with subchorionic hematoma diagnosed and one extra stillbirth occurs for every 103 women with subchorionic hematoma diagnosed. Women with subchorionic hematoma were also at increased risk of abruption (from 0.7% to 3.6%, pooled OR 5.71, 95% CI 3.91–8.33), preterm delivery (from 10.1% to 13.6%, pooled OR 1.40, 95% CI 1.18–1.68), and preterm premature rupture of membranes (from 2.3% to 3.8%, pooled OR 1.64, 95% CI 1.22–2.21), but not small for gestational age (OR 1.69, 95% CI 0.89–3.19) or pre-eclampsia (OR 1.47, 95% CI 0.37–5.89). The numbers needed to harm were 34, 28, and 69 for abruption, preterm delivery, and preterm premature rupture of membranes, respectively.Subchorionic hematoma is associated with an increased risk of early and late pregnancy loss, abruption, and preterm premature rupture of membranes.