Objective:To explore the trend of postpartum hemorrhage after two-child policy and to analyze the high-risk risks of postpartum hemorrhage so as to put forward intervention measures to reduce the postpartum hemorrhage.Methods:We retrospectively selected 8 784 delivery women with routine production inspection and hospitalized at a ClassⅢ Grade A hospital from 2014 to 2018. We collected the general information, record of production inspection, delivery record and analyzed the trend of postpartum hemorrhage rate, blood loss and related high-risk factors.Results:From 2014 to 2018, there were statistical differences in the postpartum hemorrhage rate, serious postpartum hemorrhage rate and blood loss ( P<0.05) . The trend showed an increasing trend. In 2017, the postpartum hemorrhage rate, serious postpartum hemorrhage rate and blood loss were 16.9%, 6.1% and (540.1±758.2) ml respectively highest in those years. From 2014 to 2018, the percentage of delivery women with advanced ages, multiple pregnancy, pregnancy times≥2, history of cesarean section≥2 were increasing; delivery women with the prenatal hemoglobin≤110 g/L and percentage of natural labor were decreasing with a statistical difference ( P<0.05) ; the percentage of emergency cesarean section was on the rise; the percentage of placental expulsion time from 15 to 30 minutes declined with statistical differences ( P<0.05) ; the percentage of placental expulsion time≥30 minutes and above was no significant trend. Conclusions:From 2014 to 2018, the postpartum hemorrhage rate, serious postpartum hemorrhage rate and blood loss did not show an increasing trend. However, the percentage of high-risk pregnant and delivery women increased gradually. Therefore, we should carry out the pregnancy risk assessment rating for pregnant and delivery women and formulate a suitable high-risk assessment tool for postpartum hemorrhage so as to reduce the incidence of postpartum hemorrhage.

Background In recent years, due to the increasing number of e-cigarette users, the health problems caused by e-cigarettes are attracting people's attention. Objective This study is designed to analyze the characteristics of e-cigarette-related research literature, research trends, and its toxicity from 2010 to 2020 through bibliometric analysis to provide a reference for studies related to the health effects of e-cigarettes. Methods The studies related to e-cigarettes in the Web of Science were retrieved, and the functions of "Creating citation report" and "Analyzing retrieval results" provided by Web of Science were used to conduct statistical analysis on publication time, literature type, publication source, country/region, research interests, research institution, etc. With the help of the knowledge function of CiteSpace V5.7, author collaboration, organization cooperation, keyword co-occurrence and keyword emergence, and reference co-citation were visualized. Results A total of 3094 studies related to health risks of e-cigarettes (public health) wereretrieved from 2010 to 2020, and the number of articles published between 2018 and 2020 accounted for 54.7% of total number. The top research institutions were from the United States (68.0%), the United Kingdom (7.6%), and Canada (6.1%). The most published author is King BA (67). The journal that published the most relevant studies was Nicotine Tobacco Research (536). The hot topics of e-cigarette research included "socioeconomic patterning," "multiple healthy behaviors," "expressive suppression emotion regulation strategies," "smoking cessation intervention studies" and "computer-delivered brief intervention". The burst intensity of keywords "cigarette smoking" was the highest, reaching 24.2. Between 2010 and 2020, the keywords "Nicotine dependence" and "Disease" emerged for the longest period of five years. "Policy" was the latest high-frequency word. The literature "Levels of selected carcinogens and toxicants in vapour from electronic cigarettes" was cited for the highest frequency, totaling 266 times. Conclusion The number of articles published has notably increased in 2018-2020, suggesting that researchers are paying attention to the health risks of e-cigarettes worldwide. The United States leads the world in the research of e-cigarette health risks. The future research direction will be focused on e-cigarette policy.