世界卫生组织将早产定义为在37孕周前或者259天终止者,目前在我国是指自末次月经第一日开始计算,妊娠在妊娠满28周至不满37周间分娩者称为早产。影响早产发生有多种因素,即使在一个国家的不同地区,也可由于文化水平、经济状况、医疗技术情况的不同而有差异。其发生率约在5%~15 Preterm birth is defined by WHO as terminator before 37 weeks or 259 days. Currently in our country, it is calculated from the first day of the last menstrual period. Pregnancy between 28 and 37 weeks of pregnancy is referred to as premature delivery. There are many factors that affect the incidence of preterm birth, even in different regions of a country, depending on the level of education, economic conditions and medical technology. The incidence of about 5% ~ 15