Associations of Acetylsalicylic Acid, Low-molecular-weight Heparin and Nattokinase Use with the Presence and Size of Subchorionic Hematoma in a Prospective Cohort

Abstract

Subchorionic hematoma (SCH) is a frequent ultrasound finding in early pregnancy and may be associated with adverse obstetric outcomes, particularly when larger hematomas are present. In routine practice, SCH is sometimes diagnosed in women receiving antiplatelet or anticoagulant therapy, or supplements with potential effects on haemostasis, for other clinical indications. The aim of this study was to assess the association of acetylsalicylic acid 150 mg (ASA), low-molecular-weight heparin (LMWH) and Nataspin (nattokinase-containing supplement) use with the presence of SCH and with SCH size categories. This prospective observational cohort included 462 pregnant women examined between December 2020 and July 2025: 282 controls without SCH and 180 women with SCH. Hematoma size was available in 178 women with SCH and was categorized as small (0.6–1.4 cm; n = 60), medium (1.5–2.7 cm; n = 72) or large (2.8–5.8 cm; n = 46). ASA 150 mg was more frequent among women with SCH than among controls (23.3% vs. 5.7%, p < 0.001). LMWH use was also more common in the SCH group (11.1% vs. 1.4%, p = 0.001), whereas Nataspin was less frequent (2.2% vs. 23.4%, p < 0.001). Among women with SCH, ASA use increased with hematoma size (10.0%, 22.2%, and 43.5% in small, medium and large SCH, respectively; p = 0.017). LMWH was not associated with size category. The results should be interpreted as observational associations, since treatment allocation was influenced by clinical indications.