Abstract： Objective:To explore the feasibility and key point of improvement in preventing and postponing the onset of severe pre-eclampsia (SPE) and its severe complications in the tertiary referral system by analyzing the clinical characteristics of SPE in a single tertiary referral center.Methods:The clinical data of 217 patients with SPE who were hospitalized and terminated pregnancy in Peking University Third Hospital from January 2020 to December 2020 were retrospectively analyzed. The risk factors, clinical characteristics and severe complications of SPE between the patients referred from primary hospitals (referral group) and the patients received regular prenatal care in the tertiary referral center (central group) were compared, as well as the influence of the referral timing on the characteristics and perinatal outcome.Results:(1) Clinical characteristics: among the 217 cases of SPE, 84 cases were in the referral group and 133 cases were in the central group. The gestational ages at SPE clinical diagnosis [31.5 weeks (28.1-34.6 weeks) vs 35.6 weeks (33.3-37.2 weeks); Z=-6.547, P<0.01], termination of pregnancy [32.3 weeks (29.5- 35.1 weeks) vs 36.3 weeks (34.4-37.5 weeks); Z=-6.554, P<0.01] and onset of SPE severe complications [30.6 weeks (26.4-32.7 weeks) vs 34.9 weeks (32.7-36.5 weeks); Z=-4.040, P<0.01] in the referral group were significantly earlier than those in the central group, the rates of ICU [10.7% (9/84) vs 3.8% (5/133); χ2 =4.126, P=0.042] and neonatal ICU hospitalization [72.9% (51/70) vs 54.7% (70/128); χ2 =6.286, P=0.012] were higher than those in the central group, while the live birth rate [83.3% (70/84) vs 96.2% (128/133); χ2 =10.736, P=0.001] was lower than that of the central group. (2) Analysis of risk factors: for the patient whose risk factors were obesity, advanced age or pre-eclampsia history, the gestational ages at SPE clinical diagnosis and termination of pregnancy in the referral group were significantly earlier than those in the central group ( P<0.05). For those with chronic hypertension, the gestational ages at severe complications onset in the referral group were significantly later than those in the central group ( P<0.05). For those without obvious risk factors, the gestational ages at SPE clinical diagnosis, termination of pregnancy and onset of SPE severe complications in the referral group were earlier than those in the central group ( P<0.05). (3) Analysis of severe complications: the top three severe complications in the referral group and the central group were hypertensive encephalopathy/cerebrovascular accident [20.2% (17/84) vs 7.5% (10/133)], HELLP syndrome [7.1% (6/84) vs 8.3% (11/133)] and placental abruption [8.3% (7/84) vs 7.5% (10/133)]. The rate of hypertensive encephalopathy/cerebrovascular accident in the referral group was significantly higher than that in the central group ( χ2 =7.645, P=0.006). (4) Analysis of referral timings: the timings included referral after onset of SPE severe complications (8.3%, 7/84), referral after onset of SPE (67.9%, 57/84), referral after detection of SPE early warning signs (14.3%, 12/84) and referral after detection of SPE risk factors in the 2nd and 3rd trimester (9.5%, 8/84). The earlier the referral, the longer the interval from clinical diagnosis to onset of severe complications, from referral to termination of pregnancy, and from referral to severe complications onset ( P<0.05). The earlier the referral, the lower the NICU hospitalization rates, the higher the live birth rates. The ICU hospitalization rate of referrals after severe complications onset was significantly higher than those of the other three referral timing groups ( P<0.05). Conclusions:SPE occurs in hospitals of different levels. Although tertiary referral center may postpone the onset of SPE and its severe complications, reduce the severity of SPE and prolong the gestational age, its awareness of prevention and control still needs to be further improved. Early identification of the risk of SPE and timely referral are important parts of improving SPE adverse outcomes in primary medical institutions. The significance and value of referral system need to be brought into full play.