This prospective, randomized, double-blind study compared the effects on thromboelastography (TEG) of pre-loading with two different colloid fluids prior to spinal anaesthesia for caesarean section. Healthy full-term parturients received either 500 ml 6% hydroxyethyl starch 130/0.4 (HES, n = 25) or 500 ml 4% succinylated gelatine (GEL, n = 25) prior to spinal anaesthesia. TEG parameters including reaction time (r-time), clot formation time (k-time), clot formation rate (alpha-angle) and maximum amplitude (MA) were measured immediately before and after pre-loading. Both groups had significantly shorter r-time and lower MA after pre-loading. The a-angle was significantly decreased after pre-loading with HES but not with GEL. No significant differences in k-time were induced pre-loading. In conclusion, pre-loading with HES or GEL was associated with a mild hypocoagulable effect in healthy parturients presenting for elective caesarean section; however, all TEG parameters in both groups remained within or very close to the normal range after pre-loading.