Background Unintentional injuries are major threats to children 's health，but most of them are
preventable. Since the incidence and characteristics of distribution of unintentional injuries vary across regions，it is necessary to formulate preventive measures according to local characteristics. We described systematically the incidence and characteristics of distribution of unintentional injuries in Ningbo's children.
OBJECTIVE To investigate the clinical characteristics of unintentional injuries in children in Ningbo，providing a theoretical basis for the development of relevant preventive and treatment measures.
Methods This study retrospectively recruited 0~17-year-old children with unintentional injuries（including babies，toddlers， preschoolers，gradeschoolers and teens grouped by age）from Department of Emergency，Ningbo Women and Children 's Hospital from August 2020 to July 2021. Clinical data were collected，including age，gender，registered residence，the way of getting to the hospital and pre-hospital emergency care，visit time，injury-to-admission time，places of occurrence of injury，cause of injury，site of injury，outcome of treatment，hospitalization time and hospitalization expenses. ICD-10 was used to classify the unintentional injuries. Chi-square test and Kruskal-Wallis H test were used to compare the types of unintentional injuries across the children by clinical data.
RESULTS Altogether，15 773 cases〔including 9 608 males（60.91%）〕were included，with a mean age of（5.30±3.64）years and a male to female ratio of 1.56∶1. The prevalence of unintentional injuries
in toddler age was the highest〔32.44%（5 116/15 773）〕. Children with fall/fall injuries，burns and scald，cavity foreign body，poisoning，blunt instrument injury and electric shock injuries are mainly early childhood，road traffic injuries are mainly preschool age，and sharp instrument injuries are mainly school age. Most of the children were from rural areas〔59.15%（9 329/15 773）〕. Children with rural household registration were mainly affected by falls/fall injuries，road traffic accidents， burns，foreign body aspiration，sharp instrument injuries，electric shocks and drowning. Children who suffered from falls，road traffic accidents and drowning mainly arrived at the hospital by self-driving. Children with fall/fall injuries，road traffic injuries， burns，poisoning，sharp device injuries，electric shock injuries and drowning are mainly treated without pre-hospital emergency rescue. Unintentional injuries occurred more frequently in summer（4 301/15 773，27.27%）. Road traffic injuries and burns are mainly in summer，blunt instrument injuries and electric injuries are mainly in autumn，and bites are mainly in spring and
autumn. Unintentional injuries peaked in July and bottomed in February. Visits due to unintentional injuries peaked at 12:00 at noon and 20:00 in the evening. The injury-to-admission time in children with traffic injuries was shorter than that of those with the other injuries（P<0.05）. The majority of injuries（14 396，91.27%）occurred at home. The top three causes of unintentional injuries were falls〔78.46%（12 375/15 773）〕，traffics accidents〔5.29%（12 375/15 773）〕，and burns〔3.70%（583/15 773）〕. Most unintentional injuries occurred in the head 〔31.79%（5 015/15 773）〕. Infant，preschool and school-age children mainly have head injuries，and preschool and adolescent children mainly have both upper limbs. Children with drowning had higher hospitalization rate，longer hospitalization time and higher hospitalization expenses than those with other types of unintentional injuries（P<0.05）.
CONCLUSION Among Ningbo's children，unintentional injuries，mainly including falls/
fall injuries and traffic injuries，highly occur in toddler age，with rural boys as the major suffering group，summer as the high-incidence season，and head as the major site. Different characteristics of children are associated with the type of unintentional injuries. And the type of unintentional injuries is associated with the way of getting to the hospital，injury-to-admission time，the use of pre-hospital emergency care and outcome of hospitalization. Thus，it is important to strengthen the preventive propaganda of unintentional injuries according to children's features to reduce the incidence of such injuries，and to develop rational clinical treatment strategies according to the types of unintentional injuries in children.