Baseline parameters for non-activated rotational thromboelastometry tests with and without heparinase in healthy pregnant women at term gestation.

Abstract Objective To determine the normal values for non-activated thromboelastometry parameters among pregnant women. Design Prospective, observational study. Setting Tertiary care hospital. Patients Non-laboring women at term gestation without history of bleeding or clotting disorder or anticoagulation use. Interventions Venous blood samples were collected and ROTEM® was performed using NATEM and NaHEPTEM assays. Measurements Reference ranges were derived by calculating 2.5 and 97.5 percentiles for the following parameters: clotting time (CT), clot formation time (CFT), amplitude at 10 (A10) and 20 min (A20), alpha angle, maximum clot firmness (MCF), and lysis index at 30 (LI30) and 60 min (LI60). The NATEM/NaHEPTEM CT ratio was calculated to determine the baseline ratio in term pregnant women. Main results 146 women were screened and 120 were enrolled. The median age was 34 years [31–36], median gestational age was 39.1 weeks [38.3–39.3], and median parity was 1 [0–2]. Median pre-delivery platelet and hematocrit levels were within the normal ranges. The reference ranges for NATEM parameters were: CT (232–759 (s)), CFT (69–243 (s)), alpha angle (50–77 (°)), A10 (44–69 (mm)), A20 (54–75 (mm)), MCF (57–77 (mm)), LI30 (100–100 (%)), LI60 (90–100 (%)). The reference ranges for NaHEPTEM parameters were: CT (224–717 (s)), CFT (66–210 (s)), alpha angle (53–77 (°)), A10 (44–67 (mm)), A20 (55–73 (mm)), MCF (58–74 (mm)), LI30 (99–100 (%)), LI60 (90–100 (%)). The NATEM to NaHEPTEM CT ratio reference range was 0.73–1.3. Conclusions This study is the first to our knowledge to report reference ranges for non-activated ROTEM® tests with and without heparinase in non-laboring term pregnant women. These reference ranges may serve as a baseline comparison and may be useful for future research on anticoagulation management in pregnancy.