Postpartum hemorrhage (PPH) is the most significant leading cause of pregnancy-related mortality in high-risk cesarean delivery women. Systemic autoimmune diseases are associated with adverse pregnancy outcomes (APOs), including PPH, preeclampsia, thromboembolism, abortion, and intrauterine growth restriction. The incidence of PPH in women with systemic lupus erythematosus has been reported to be as high as 34%. Prevention of PPH is the key to reduce complications in high-risk women. In recent years, a large number of clinical studies have confirmed that the early preventive use of tranexamic acid(TXA) can reduce the amount of blood loss, the need for additional uterine contraction agents, the risk of blood transfusion, and maternal adverse outcomes, and do not increase the risk of thromboembolic events, which can be used to prevent PPH. However, the study population of TXA is mainly low-risk puerpera, and there is still a lack of relevant research on TXA used in pregnant women with systemic autoimmune diseases. The purpose of this study was to evaluate the safety and efficacy of TXA in preventing postpartum hemorrhage after cesarean delivery in women with systemic autoimmune disease, as well as the maternal and neonatal risks associated with systemic autoimmune disease, to provide evidence for clinical practice and further research.

The worldwide estimated cumulative prevalence of autoimmune disease is approximately 5%. Studies are often limited by small sample sizes and focused on a specific autoimmune disease such as systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS), which is characterized by the production of autoantibodies leading to inflammation of multiple organs. Systemic autoimmune diseases are associated with adverse pregnancy outcomes (APOs), including increased cesarean delivery rates, PPH, preeclampsia, thromboembolism, abortion, premature delivery, and intrauterine growth restriction. Preeclampsia is the most commonly reported complication in patients with SLE and is also a high risk factor for PPH. The incidence of PPH in women with SLE has been reported to be as high as 34%. PPH increases the need for blood transfusion and related complications and is a significant clinical and socio-economic problem. Therefore, prevention of PPH is the key to reduce the postpartum complications of high-risk women. At present, the methods commonly used to prevent PPH after cesarean delivery include uterine massage, prophylactic use of uterine contraction agents in the third stage of labor, and early use of TXA. Recent clinical studies of TXA use in high-risk cesarean delivery women have shown that prophylactic use of TXA significantly reduces blood loss, prevents PPH, and reduces ICU admission and length of stay. There was no evidence of an increased risk of maternal-related complications with TXA use. But there is still a lack of relevant research on TXA used in pregnant women with systemic autoimmune diseases. Anti-phospholipid antibodies (aPL) are often present in SLE and APS patients, which predict serious perinatal complications and are associated with the risk of thrombosis. aPL are detected not only in SLE and APS but also in other connective tissue diseases such as systemic sclerosis (SSc), Sjögren's syndrome (SS), rheumatoid arthritis (RA), and undifferentiated connective tissue disease (UCTD). Although TXA has been widely used in patients at high risk for thromboembolism, such as trauma, orthopedics, and cardiac surgery in recent years, the evidence strongly supports that it does not increase the risk of death or thromboembolic complications. More evidence from high quality randomized controlled trials is needed to assess the benefits and risks of its use in women at high risk of PPH after cesarean delivery.

The aim of this study was to evaluate the safety and efficacy of TXA in preventing PPH after cesarean delivery in women with systemic autoimmune disease. Patients undergoing cesarean delivery were randomly assigned to TXA group(intravenous infusion of TXA 1g (20ml) 10min before skin dissection) and placebo group(intravenous infusion of normal saline 20ml 10min before skin dissection).The estimated blood loss 24h postoperatively, blood transfusion 3d postpartum, additional uterotonics, other surgical intervention for PPH and thromboembolic events were recorded.

Inclusion Criteria:

1. Patients undergoing cesarean delivery
2. Preoperative diagnosis of pregnancy with systemic autoimmune diseases (systemic lupus erythematosus, antiphospholipid syndrome, systemic sclerosis, Sjogren's syndrome, rheumatoid arthritis, undifferentiated connective tissue disease)
3. Obtain informed consent.

Exclusion Criteria:

1. intrauterine fetal death
2. Existing/previous history of thromboembolism
3. Hemorrhagic disease, significant prenatal bleeding
4. Balloon placement of internal iliac artery
5. Allergic to tranexamic acid
6. Severe renal insufficiency (serum creatinine >451μmol/L or blood urea nitrogen >20mmol/L)
7. Epilepsy