RSA patients are often accompanied by a tendency of thrombosis. To study the effect of PTS on the pathogenesis of RSA may be of great significance for the early prevention and intervention of RSA. However, thrombotic diseases often lack obvious clinical symptoms and signs before their occurrence or in the early stage of their formation, so prediction and early diagnosis are rather difficult. Logistics regression analysis is a generalized linear regression analysis model, which can be used to explore the risk factors of disease occurrence and predict the probability of disease occurrence according to the risk factors. Some scholars have applied it to the etiology research of RSA.7 In this study, multivariate Logistic regression was used to assess the influence of important markers of PTS on the occurrence of RSA. The ROC curve evaluation model showed good simulation degree. It was finally concluded that BMI, PAI-1(675) and MTHFR(677) gene locus polymorphism were risk factors for RSA.
PTS-related genetic markers in patients with RSA
The most common pathogenesis of hereditary PTS in western populations is FV mutation, followed by F II mutation. The mutated FV can not only continue to express procoagulant activity, but also decrease the cleavage ability of activated protein C, thereby generating activated protein C resistance, manifested as PTS8. The research by Poort et al has shown that the G-A conversion of nucleotide 20210 at the 3' untranslated region of coagulation F II can increase the plasma prothrombin level of the body, 9 thus causing venous thromboembolic diseases. In this study, no F V 1691 or F II 20210 polymorphic mutation was found in the tested women, 10 suggesting that Chinese women with RSA have rare F V 1691 or F II 20210 polymorphic mutations in prethrombotic state. This may be due to the uneven distribution of PTS across ethnic groups and regions.
PAI-1 is the main inhibitor of plasma fibrinolytic system and the main substance that inhibits fibrinolytic activity in the blood circulation. The increased level of PAI-1 leads to the decreased fibrinolytic activity and enhanced coagulation process. It is one of the risk factors for thrombotic diseases. Sheppard believed that PAI-1 expression products increased the deposition of vascular fibrin in endometrium during early pregnancy, and decreased uterine and placental blood flow, resulting in abortion.14 Glueck et al found that the PAI-1 (-675) 4g/5g polymorphism was the susceptible genotype for unexplained recurrent spontaneous abortion and had a strong independent correlation with adverse pregnancy outcomes.15 In this study, we found that PAI-1(675) was closely related to RSA in a multi-factor regression analysis (P < 0.05; OR=1.508), indicating that the PAI-1(675) locus polymorphism was an independent risk factor for RSA.
MTHFR and MTRR are the two most important genes in folic acid metabolism. The mutation at site 677 of MTHFR gene and the mutation at site 66 of MTRR gene at site 1298 make the serum HCY level too high and have a direct toxic effect on the embryo, which can damage the vascular endothelium, stimulate the proliferation of vascular smooth muscle cells, and lead to the imbalance of coagulation and fibrinolysis in the body.16 The results of this study suggested a correlation between the MTHFR(677) locus polymorphism and RSA (P<0.05), but no correlation was found between the MTHFR(1298) locus polymorphism and RSA (P > 0.05), which was consistent with the results of a meta-analysis.17
PTS related coagulation markers in RSA patients
The most common genetic factor in the Han population is congenital anticoagulant protein deficiency, including protein C, protein S and antithrombin, mainly PC or PS, and antithrombin deficiency is rare.11 Because the levels of PC and PS fluctuate significantly during pregnancy, it is more reliable to monitor the nonpregnant levels in women. 12 In this study, the χ2 test showed that both PC defects and PS defects had no correlation with RSA (P > 0.05). However, the positive rate of PS defects in the case group (21.8%) was significantly higher than the incidence rate of PS defects in the control group (14.5%), which might be related to the insufficient sample size in this study. Therefore, the correlation between PC and PS defects and RSA needs further large sample data analysis.
Some studies have suggested that the increase of HCY is closely related to RSA, and its mechanism may be related to coagulation abnormalities. The main reason for the increase of HCY is folic acid deficiency. After standardized folic acid intervention, the metabolism of folic acid can be regulated to reduce the level of HCY. 18,19 In this study, no correlation was found between HCY and RSA, which might be related to the increased publicity of the national policy of free folic acid distribution, the increased awareness of pre-pregnancy health care for women of childbearing age in the region, and the adequate supplementation of folic acid during the pre-pregnancy period.
Some studies have suggested that the increase of BMI is related to the increased risk of spontaneous abortion,13and its molecular mechanism may be that excessive insulin acts on the ovarian theca cells through insulin receptors to affect the embryo implantation. Logistic regression analysis in this study showed that the OR value of BMI was 3.264, which meant that for every 1 kg/m2 increase in body mass index after other factors were controlled, the probability of illness was 3.264 times the original one. Therefore, controlling reasonable BMI might reduce the risk of illness of RSA.