Variations of coagulation biochemical markers in normal pregnant women in early and late pregnancy

Objective To investigate the changes of coagulation indexes in normal pregnant women in early and late pregnancy. Methods The coagulation indexes in early and late pregnancy including activated partial thromboplastin time (APTT), APTT ratio, prothrombin time (PT), PT ratio, prothrombin activity, international normalized ratio, fibrinogen (Fib) and thrombin time (TT) were retrospectively collected from 196 normal pregnant women delivered in Peking University First Hospital from August 2013 to September 2014. Differences in these indexes before and after the seventh gestational week of early pregnancy and in early and late pregnancy were compared. In addition, the normal reference values were calculated. Paired t test and sum-rank test were used for statistical analysis. The reference values were presented with P2.5-P97.5. Results In early pregnancy, some coagulation indexes after the seventh weeks were shorter than those before, such as APTT [30.3 (26.1-35.5) vs 32.1 (27.9-36.8) s, Z=25.850, P<0.001] and TT [13.8 (12.2-16.0) vs 14.5 (12.3-16.4) s, Z=16.720, P<0.001], but Fib [3.3 (2.5-4.3) vs 2.9 (2.2-3.8) g/L, Z=43.180, P<0.001] became higher. APTT [(27.5±1.6) vs (31.4±2.4) s, t=24.736, P<0.001], PT [(9.7±0.5) vs (11.0±0.8) s, t=18.647, P<0.001] and TT [(13.3±0.8) vs (14.2±1.0) s, t=9.255, P<0.001] were significantly shorter, while Fib [(4.4±0.5) vs (3.1±0.4) g/L, t=-29.152, P<0.001] was higher in late pregnancy than in early pregnancy. The reference values of APTT, PT, Fib and TT in early pregnancy were 26.5-36.0 s, 9.4-12.4 s, 2.4-4.0 g/L and 12.3-16.4 s, and those in late pregnancy were 25.0-31.2 s, 8.8-10.6 s, 3.4-5.4 g/L and 12.0-14.9 s, respectively. Conclusions The coagulation indexes of pregnant women change significantly since the beginning of early pregnancy. APTT, PT and TT are shorter, while Fib is higher in late pregnancy than in early pregnancy. Key words: Partial thromboplastin time; Prothrombin time; Thrombin time; Fibrinogen; Pregnancy trimester, first; Pregnancy trimester, third