BackgroundAntenatal depression (AD) is a major depressive disorder during pregnancy, which may lead to devastating sequelae for the expectant mothers and infants. This study aimed to investigate the prevalence, to analyze trajectory model based on EPDS score,and to explore the influence factors of AD among pregnant women in Chengdu, China.MethodsParticipants from four maternity hospitals in Chengdu, China were recruited when they had their first pregnancy medical check-up during March 2019 to May 2020. All participants were required to fill in Edinburgh Postnatal Depression Scale Chinese version (EPDS) once during three trimesters and provided information about their health status, social-demographic etc. The trajectory model, chi-square test and multivariate binary logistic regression were used to analyze all collected data.ResultsA total of 4560 pregnant women were recruited, while 1051 women completed the study. The prevalence of depression symptoms during the first, second and third trimesters were 32.92% (346/1051), 19.79% (208/1051) and 20.46% (215/1051) respectively. According to the results of the latent growth mixture modeling, the trajectory model of three categories based on EPDS score were identified in this study: low-risk group (38.2%, 401/1051), medium-risk group (54.8%, 576/1051) and high-risk group (7%, 74/1051). Good marital relationship (P= 0.007, OR = 0.33, 95%CI0.147 ~ 0.74), good relationship with parents-in-law (P= 0.011, OR = 0.561, 95%CI0.36 ~ 0.874), planned pregnancy (P= 0.018, OR = 0.681, 95%CI0.496 ~ 0.936) were the protective factors while lower education level (P= 0.036, OR = 1.355, 95%CI1.02 ~ 1.799), fear about dystocia (P= 0.0, OR = 1.729, 95%CI1.31 ~ 2.283), recent major negative life events (P= 0.033, OR = 2.147, 95%CI1.065 ~ 4.329) were the risk factors of medium-risk group. Good marital relationship (P= 0.005, OR = 0.2, 95%CI0.065 ~ 0.615), good relationship with parents-in-law (P= 0.003, OR = 0.319, 95%CI0.15 ~ 0.679) were also protective factors of high-risk group, but the risk factors for high-risk group were medical history (P= 0.046, OR = 1.836, 95%CI1.011 ~ 3.334), pregnancy complications (P= 0.022, OR = 2.015, 95%CI1.109 ~ 3.662), worry about dystocia (P= 0.003, OR = 2.365, 95%CI1.347 ~ 4.153), recent major negative life events (P= 0.011, OR = 3.661, 95%CI1.341 ~ 9.993). No protective or risk factors were identified for low-risk group.ConclusionEven the incidence and levels of depression in the first trimester of pregnancy were the highest, the probability of pregnancy women get depression during gestation period were higher than other population. Therefore, it’s important to monitor the psychological status of pregnant women during the whole pregnancy, especially in the first trimester. The study suggested a good partner relationship and good relations with parents-in-law both protected pregnant women from depression and promoted the well-being of mothers and children.