Coagulation changes during pregnancy and delivery: adjustment of reference ranges for thrombelastography and for some laboratory tests is necessary

Hypothesis

The coagulation status in pregnant women is different from the general population in so far that we must adjust the reference range of coagulation tests for these women.

Objective

To compare the coagulation parameters in pregnant and parturient women to normal ranges used for the general population. If there is a significant difference between these groups, set new ranges for thrombelastography and/or coagulation laboratory tests.

Participants

Sixty healthy pregnant women (group HPW) were divided into two subgroups: 30 in the third trimester (subgroup TT) and 30 in the first period of delivery (subgroup FP).

Design and methods

A prospective nonintervention study. In all women we performed thrombelastography and coagulation laboratory tests. Thrombelastography was performed from native blood after activation by 1% cellite. Blood samples were obtained from the peripheral vein, before any medical intervention.

Results

The mean of all thrombelastographic parameters in the HPW group was in the normal range set for the general population, but mostly very close to a 'procoagulation' limit (mean time r 4.7 ± 1.7; time k 1.5 ± 0.5; alpha angle 69.6 ± 5.5; maximal amplitude 71.3 ± 4.5; coagulation index 2.7 ± 1.8); there was no statistically significant difference between subgroups TT and FP. In laboratory tests, the majority of parameters was also close to the 'procoagulation' limit of the normal range and, in addition, three of the parameters were outside the normal range (mean fibrinogen 5.2 ± 0.6; D-dimers 349.9 ± 138.6; protein S 42.4 ± 13.7). After the statistical analysis we adjusted the reference ranges for pregnant women. Some of our recommendations for thrombelastography are presented in Table 1.

Table 1

Conclusions

For assessment of coagulation status by thrombelastography and for some laboratory tests in pregnant and parturient women, it is necessary to set new reference ranges that are different from those for the normal population.