Trimester-specific coagulation and anticoagulation reference intervals for healthy pregnancy

Due to the normal physiological need of pregnancy and childbirth, the haemostatic system of pregnant women is different from that of healthy non-pregnant women. The aim of this study was to establish trimester-specific reference intervals of coagulation screening tests and thrombophilia markers in pregnancies without complications of females with Han ethnicity from North China.

In total 744 Han healthy pregnant women (first trimester 207 cases, second trimester 222 cases and third trimester 315 cases) and 121 healthy non-pregnant women were recruited in North China. Eight tests-activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen (Fib), d-Dimer, antithrombin (AT), protein C (PC) and free protein S (fPS)-were processed on ACL TOP automated coagulation analyzer. The non-parametric 2.5th-97.5th percentiles reference intervals were calculated to establish trimester-specific reference intervals.

The reference intervals for APTT, PT, TT, Fib, d-Dimer, AT, PC, and fPS at first trimester were 26.4-41.9s, 9.7-12.5s, 11.7-17.0s, 2.38-4.44g/L, 0.01-0.31μg/mL, 72-120%, 29-150%, 21-143%, respectively. At second trimester, the reference intervals were 24.4-35.8s, 8.5-13.2s, 10.0-16.0s, 2.40-5.97g/L, 0.05-0.73μg/mL, 68-125%, 20-138%, 24-155%, respectively. At third trimester, the reference intervals were 25.6-34.9s, 8.6-12.4s, 11.1-15.5s, 2.79-5.91g/L, 0.14-2.82μg/mL, 56-119%, 20-134%, 17-140%, respectively. From the first trimester to the third trimester, APTT, PT and TT presented shortened trends, Fib and d-Dimer presented increasing trends, AT, PC and fPS activity presented decreasing trends, respectively.

The trimester-specific reference intervals of coagulation screening tests and thrombophilia markers in pregnancies without complications of females with Han ethnicity from North China are presented in this study, which may provide effective evidence for doctors to accurately diagnose and treat the disease during pregnancy.