Abstract: Objective To investigate the relationship between vascular endothelial growth factor (VEGF), micro-vascular density (MVD), helper T cells 17 (Th17)/ regulatory T cells (Treg)and the degree of placenta accreta complicated by infection and to predict the prognostic value. 
Methods In total, 50 patients with placenta accreta complicated by infection admitted to our hospital were selected as the observation group, including 20 cases with mild, 17 cases with moderate and 13 cases with severe disease, and another 50 patients with placenta accreta but without complicated infection during the same period were selected as the control group. The patients were divided into good prognosis (n=29) and poor prognosis (n=21) according to pregnancy outcome. VEGF, MVD, and Th17/Treg were compared between two groups, and VEGF, MVD, and Th17/Treg were analyzed in relation to conventional infection markers ［interleukin-6 (IL-6), C-reactive protein (CRP), procalcitonin (PCT)］ and the severity of placenta accreta complicated by infection. The clinical data, VEGF, MVD, and Th17/Treg in patients with different prognoses were compared, to analyze the prognostic factors, and to evaluate the predictive value of VEGF, MVD, and Th17/Treg in the prognosis of patients with placenta accreta complicated by infection. 
Results The levels of VEGF, MVD and Th17/Treg in the observation group were higher than those in the control group (P＜0.05); VEGF, MVD and Th17/Treg in patients with placenta accreta complicated by infection were positively correlated with the severity of placenta accreta complicated by infection (P＜0.05). The levels of VEGF, MVD and Th17/Treg in patients with poor prognosis were higher than those in patients with good prognosis (P＜0.05). Logistic regression equation showed that after adjusting for confounding factors such as age and gestational age, VEGF, MVD and Th17/Treg were still independent risk factors for the poor diagnosis of patients with placenta accreta complicated by infection (P＜0.05). Receiver operating characteristic (ROC) curve was drawn, and the results showed that the area under the ROC curve (AUC) of VEGF, MVD and Th17/Treg for predicting the prognosis of patients with placenta accreta complicated by infection was 0.541 (95%CI: 0.388-0.689), 0.813(95%CI: 0.671-0.913), and 0.766 (95%CI: 0.618-0.878), respectively. Logistic binary regression fitting was applied to construct the AUC for the combined diagnosis of each index, and the results showed that the AUC for the combined index was 0.890 (95%CI: 0.763-0.963), with a sensitivity of 90.48% and a specificity of 84.00%. The correlation analysis of conventional infection markers PCT (2.76±0.58) μg/L, CRP (48.23±15.84) mg/L and IL-6 (124.38±29.26) ng/L in patients with placenta accreta complicated by infection showed that VEGF, MVD and Th17/Treg were positively correlated with PCT, CRP and IL-6 levels (P＜0.05). 
Conclusion VEGF, MVD, Th17/Treg are significantly increased in patients with placenta accreta complicated by infection, and are closely related to the severity of infection and prognosis. Clinical detection of their levels is helpful for disease assessment and prognosis prediction. 

Key words: placenta accreta, severity of infection, prognosis