Gestational Week Related Changes And Reference Ranges For Routine Coagulation Tests

Objective: 1) To study the changes and reference ranges for routine coagulation tests during the normal pregnant trimesters; 2) To establish gestational week related reference ranges for those coagulation tests, if their changes are both statistical and clinical significant with normal pregnant trimesters through a longitudinal study.Methods: 242 nulliparous pregnant women were investigated during this longitudinal study, which were the first trimester and from West China Second University Hospital, Sichuan University during April to September 2005.They were been examined for PT,INR,APTT,APTT Ratio, PLT,MPV,Fg and FDP coagulation tests during each trimester and 12 weeks postpartum. The real normal pregnant women 155 were defined as those, which had the normal outcomes during their whole pregnancy, delivery and 12 weeks after delivery, including their neonates. 53 healthy non-pregnant women were the control. Informed consent was obtained from each of both pregnant and non-pregnant women investigated in this study. Gestational trimester related reference ranges and changes of coagulation tests were described as the median, 2.5 and 97.5 centiles, and then gestational week related reference ranges as equations through curve estimation methods. Results: 1) PT, INR, APTT and APTT Ratio were decreased (P＜0.05), but no clinical significant with normal gestation trimesters compared with the control. PLT and MPV were no changes. Both Fg and FDP concentrations were gradually increased with normal gestation compared with the control (P＜0.05), which were also clinical significant.2) The first, second and the third trimester related references ranges for PT were 11.8 (10.6-12.9),11.5 (10.5-12.5) and 11.6 (10.7-12.7) respectively; INR were 0.94 (0.84-1.03), 0.90 (0.82-1.00) and 0.91 (0.84-1.00) respectively; APTT were 28.7 (23.0-27.1), 26.9 (22.9-33.4) and 26.7 (22.6-32.8) second respectively; APTT Ratio were 1.01 (0.84-1.23), 0.94 (0.82-1.14) and 0.91(0.77-1.10) respectively; PLTwere 151(77-256), 144 (73-255) and 138 (78-241) 10⁹/L respectively; MPV were 12.6 (10.1-15.1), 12.6 (9.7-14.5) and 12.6 (9.6-14.5) fl respectively; Fg were 360(274-515), 368(270-556) and 421(271-598)mg/dl respectively; and FDP were 2.76 (1.69-4.01), 3.30 (2.02-6.21) and 4.35 (2.56-9.88) ug/ml respectively.3) Gestational week related reference ranges for Fg and FDP were as the followings:Fg median = 0.3182gestational week ² - 10.338gestational week + 430.57Fg 2.5 centiles = 0.0253gestational week ² + 2.964gestational week + 192.37Fg 97.5 centiles = 0.2005gestational week ²-2.073gestational week + 437.82 FDP median = 1.9881e^{0.0248gestational week}FDP 2.5 centile = 1.1555e^{0.0241 gestational week}FDP 97.5 centile = 2.4658e^{0.0384 gestational week}Conclusion: (1) It indicates that normal pregnancy were women with a characteristics of physiological hypercoagulable state that the changes for routine coagulation tests with gestational trimesters, because coagulation activities are increased, especially Fg. On the other hand, the fibronolysis activities (FDP) also are increased with increase of Fg, which may focus on the control Fg to a high level but no microthrombus in a pregnant woman. (2) Both Fg and FDP concentrations are gradually increased with normal gestation compared with the control, which are both statistical and clinical significant. Therefore, it is very important to establish a gestational week related reference ranges for Fg and FDP to obstetricians'making clinical decisions. No gestational trimesters and week related reference ranges are needed for PT, INR, APTT, APTT Ratio, PLT and MPV.