Association between graded subchorionic hematoma and adverse pregnancy outcomes in singleton pregnancies: a prospective observational cohort study.

Objective: To investigate whether different grades of subchorionic hematoma (SCH) are involved in the timing of birth and the development of adverse pregnancy outcomes in singleton pregnant women.

Methods: A total of 171 women with singleton pregnancies, 72 of whom had SCH before 20 weeks and between 12 and 20 weeks of gestational age (GA), were included in this study conducted between January 2018 and December 2021. These patients were divided into three subgroups based on the size of the subchorionic hematoma on ultrasound imaging. Baseline demographic data, obstetric outcomes, and risk factors for subchorionic hematoma were compared for the two groups.

Results: A higher number of pregnancies from the SCH group resulted in miscarriage (30.56% versus 2.02%, p < 0.0001), early preterm birth (8.33% versus 1.01%, p = 0.0035), premature rupture of membranes (15.28% versus 4.04%, p = 0.0103), fetal growth restriction (9.72% versus 0%, p = 0.0015), and delivery 13.18 days earlier (274.34 ± 11.25 versus 261.16 ± 29.80, p = 0.0013) than those from the control group. Compared with SCH detected before 12 weeks of GA, the rate of miscarriage increased, and the live birth rate decreased significantly in patients with SCH caught between 12 and 20 weeks of GA. With the increase in hematoma size, the likelihood of miscarriage increased significantly. Further analysis found that delivery occurred earlier in the medium/large SCH group (271.49 ± 23.61 versus 253.28 ± 40.68/261.77 ± 22.11, p = 0.0004/0.0073) but not in the small SCH group (274.34 ± 11.25 versus 267.85 ± 21.01, p = 0.2681) compared to the control group. Our results also showed that the anterior placenta (52.04% versus 33.33%, p = 0.0005, OR = 0.3137, 95% CI [0.1585, 0.601]) is a protective factor for subchorionic hematoma.

Conclusion: Our study shows that women with SCH are at a higher risk of adverse pregnancy outcomes and are independently associated with miscarriage, early preterm birth, premature rupture of membranes, and fetal growth restriction. A subchorionic hematoma, especially detected between 12 and 20 weeks of GA, is very likely to cause miscarriage or preterm birth in women with a medium or large subchorionic hematoma.