Risk stratification according to genotype and effect of thromboprophylaxis on obstetric outcomes in women with antithrombin deficiency

Background: Hereditary antithrombin (AT) deficiency is a risk factor for venous thromboembolism (VTE) and for obstetric complications and warrants thromboprophylaxis in certain situations. AT deficiency is divided into subtypes with different risk profiles. There is limited knowledge on the specific risks in pregnant women depending on the subtypes. Objectives: The study aim was to investigate whether genotyping pregnant women with AT deficiency could aid in determining complication risk and subsequently help to individualize antepartum and postpartum treatment. Methods: This retrospective cohort study included 43 women with AT deficiency with 106 (61 treated, 40 untreated, and 5 unknown) pregnancies between 1990 and 2022 managed at Karolinska University Hospital. Data were gathered on maternal characteristics, heredity and a history of VTE, thrombophilias, treatment during pregnancy, and maternal and neonatal outcome. Results: = .014). We did not find a statistically significant difference in incidence of VTE or other pregnancy complications between the high-risk and low-risk groups. Conclusion: Our results suggest that untreated women with type IIHBS have a high risk of pregnancy complications, which might warrant thromboprophylaxis regardless of VTE risk.