Estimating the risk thresholds used by guidelines to recommend postpartum thromboprophylaxis.

Background Guidelines for postpartum thromboprophylaxis are mostly expert based. Acceptable postpartum venous thromboembolism (VTE) risk thresholds to justify the use of thromboprophylaxis are ill defined. Objective To compare the proportion of postpartum women with recommended thromboprophylaxis according to the Royal College of Obstetricians and Gynecologists (RCOG), American College of Obstetricians and Gynecologists (ACOG), and American College of Chest Physicians (ACCP) guidelines, and to estimate their threshold of risk of VTE. Methods We collected maternal, obstetrical, and fetal characteristics among all women who delivered at the Geneva University Hospitals in January 2019 through medical chart review. We determined for each woman the recommended strategy of thromboprophylaxis according to each guideline. We indirectly estimated individual absolute VTE risks using a validated risk prediction model (Sultan). Results Among 344 women (mean age 32.2 years), with 23.3% of cesarean deliveries (CD), the RCOG guideline categorized 40.1% of all deliveries, 25.4% of vaginal deliveries (VD), and 88.8% of CD as requiring thromboprophylaxis. The ACOG and ACCP guidelines, which focus on CD, categorized fewer women as high risk (35.0% and 40.0% of CD, respectively). The mean estimated risk of VTE was 0.07% in all participants, 0.12% in those with recommended thromboprophylaxis according to the RCOG, and 0.20% among women after CD with recommended thromboprophylaxis by the ACOG and ACCP guidelines. Conclusions Our data highlight important variations in the proportion of thromboprophylaxis recommendation between guidelines. Risk thresholds to recommend the use of heparin appear very low, and may correlate with a high, and perhaps undesirable, number needed to treat to prevent VTE events.