The Study On Activated Protein C Resistance And Factor V Leiden Mutation In Patients With Recurrent Spontaneous Abortion

Objective:A successful outcome of pregnancy requires an efficient uteroplacental vascular system.Thrombosis of placental vessels can be a major cause of recurrent spontaneous abortion.The balance between procoagulant and anticoagulant mechanisms in the circulation is dependent on the protein C system,which provides anticoagulant properties integral to limiting clot formation. Activated protein C selectively degrades the coagulation factors Va and VIIIa.A commen missense mutation in the factor V gene,the Leiden mutation,renders factor Va resistant to cleavage inactivation by activated protein C and predisposes patients to thrombotic events.Recent results demonstrated that inherited and acquired thrombophilia were associated with recurrent spontaneous abortion.We sought to study whether activated protein C resistance (APCR) and factor V Leiden mutation were associated with Chinese Han's recurrent spontaneous abortion.Methods: The study population comprised 34 nonpregnant parous women (control group) and 42 patients with recurrent spontaneous abortion. Blood sample werecollected,separated,and stored at -70 until assay. Response to activated protein C was detected by activated partial thromboplastin time (APTT) in the presence and absence of APC.Activated protein C sensitivity ratio ^2.18 indicated resistance to APC.Deoxyribonucleic acid was extracted from whole blood of 10 women with resistance to activated protein C.The polymerase chain reaction was used to amplify exon 10 of the factor V gene,followed by enzymatic digestion with Mnl I for mutation detection.Statistical analysis of the data were performed with use of unpaired / test comparing various parameters in all groups. And results of the APC positive rate were analyzed a x2 contingency table.A P value <0.05 was considered statistically significant.Results:1.When APC was added to plasma from 34 controls,the mean APTT prolongation was 64+10.77 seconds,in patients group the mean APTT prolongation was 50+18.47 seconds.There was significant difference for mean APTT prolongation between controls and the patients(P<0.001).2.APCR was found in 21.43% of women with recurrent spontaneous abortion and in around 2.94% of control groups.There was significant difference for APCR between controls and the patients(P<0.05).The mean activated protein C sensitivity ratios were significantly lower in the patients group with recurrent spontaneous abortion than in healthy controls(2.31+0.41 and 2.64+0.23 respectively, P<0.001).Thus,in all evaluated women withseveral pregnancy losses,the prevalence of resistance to activated protein C was increased 7.3-fold.3.Among the study group,the prevalence of APCR positive rate in recurrent fetal losses with two times was 20%,and the positive rate in three or more successive losses was 22.22%. No significance was observed in the prevalence of APCR in women with different numbers abortion(P>0.05).4.The positive rate of APCR in patients with late abortion was 38.89%, and that with only early abortion was 8.33%.There was significant difference for APCR between late abortion and early abortion(P<0.05). There was significant difference for APCR between controls and late abortion(P<0.001). There was no difference for APCR between controls and early abortion(P>0.05).5.Allele-specific polymerase chain reaction analysis demonstrated that none of the activated protein C resistance women carried the factor V Leiden mutation.Conclusion:1.The resistance to activated protein C may play a considerable role for women having recurrent spontaneous abortion,and factor V Leiden mutation had no relation to the patients.2.The prevalence of APCR positive rate had no relation to the numbers of abortion.3.The prevalence of APCR in women with late abortion is significantly higher than that of only early abortion.4.In Chinese Han's people factor V Leiden mutation may not be the main cause of APCR.