The influence of obesity on coagulation in healthy term pregnancy as assessed by rotational thromboelastometry

Background: Rotational thromboelastometry (ROTEM^® ) is a point-of-care coagulation test which has been used to demonstrate hypercoagulability in pregnant populations and obese populations.

Aim: The aim of this study was to assess the combined effect of pregnancy and obesity on coagulation using ROTEM^® in healthy pregnant women of varying body mass indices (BMIs) presenting for elective caesarean delivery.

Materials and methods: Ethics approval was granted for recruitment of women presenting for elective caesarean delivery. Women with any condition affecting coagulation were excluded. The ROTEM^® parameters of extrinsically activated thromboelastometric test / fibrin polymerisation test (EXTEM/FIBTEM) amplitude at five minutes (A5), coagulation time (CT), maximum clot firmness (MCF) and clot formation time (CFT) were compared between three different groups: normal weight, overweight and obese women.

Results: One hundred and eighty-five women presenting for elective caesarean delivery met inclusion criteria and were divided into three groups; normal weight (BMI < 25 kg/m² , n = 86), overweight (BMI 25-29.9 kg/m² , n = 54) and obese (BMI ≥ 30 kg/m² , n = 45). They had a mean (SD) age of 32.7 ± 5.0 years and the median (interquartile range) BMI of 21.9 kg/m² (20.5-23.0), 27.0 kg/m² (26.0-28.5), 36.0 kg/m² (32.2-41.8) for the normal weight, overweight and obese groups respectively. Forty-one (22.2%) women were nulliparous. Across the three groups for FIBTEM A5 (P = 0.018), FIBTEM MCF (P = 0.032), FIBTEM CFT (P = 0.047) and EXTEM MCF (P = 0.015) there was evidence of increasing coagulability with increasing BMI. However, following Bonferroni correction, this was no longer significant.

Conclusions: There is no association between BMI and ROTEM^® parameters in pregnant women presenting for elective caesarean delivery at term.