Abstract: Background　Neonatal birth weight is an important index to measure the growth and development of fetus in the uterus,and it plays an important role in predicting the health condition,growth and development of the newborn in childhood.There are many studies exploring the risk factors of low birth weight and macrosomia,however,there are few studies collecting data in large cities like Beijing.Objective　To investigate the distribution of neonatal birth weight in Beijing,and analyze the risk factors that affect the incidence of low birth weight and macrosomia.Methods　We selected the infants born in 2014 with certificate of live birth from medical birth information database of Beijing maternal and child health information system,and extracted their medical information,including newborn’s gender,birth weight，gestational age at birth,region of birth,and mother’s maternal age,fetal number and place of household registry.Results　We collected 269 609 cases of newborns’ medical information.The average birth weight of the newborn boys was （3 398±489）g,and that of girls was （3 294±471）g.There were 10 753 （3.99%） cases of newborns with low birth weight and 21 685（8.04%） cases with macrosomia.The incidences of low birth weight and macrosomia between different newborn’s gender,gestational age at birth and region of birth were significantly different （P<0.05）;the incidences of low birth weight and macrosomia between different mother’s maternal age,fetal number and place of household registry were also significantly different （P<0.05）.The results of multivariate Logistic regression analysis indicated that girl,premature infant,born in urban area,maternal age below 25 years old and multiple fetuses were the risk factors for low birth weight;boy,postmature infant,born in suburb or exurb,maternal age over 34 years old,single fetus and non-Beijing household registrant were the risk factors for macrosomia（P<0.05）.Conclusion　The incidence of low birth weight is relatively low,whereas that of macrosomia is relatively high in Beijing for the year 2014.Newborn’s gender,gestational age at birth,region of birth，mother’s maternal age and fetal number are the root causes for newborn’s abnormal birth weight.

Key words: Infant,low birth weight, Fetal macrosomia, Root cause analysis, Beijing

摘要： 背景　新生儿出生体质量是衡量胎儿子宫内生长发育的重要指标，并对新生儿在儿童期的健康状况和生长发育有重要预示作用。目前，针对北京市的大范围低出生体质量儿和巨大儿发生现状及其影响因素研究有限。目的　通过分析2014年北京市新生儿出生体质量分布，探讨低出生体质量儿和巨大儿发生的影响因素。方法　选取北京市妇幼保健信息系统出生医学信息数据库中2014年出生并签发出生医学证明的新生儿，提取新生儿医学信息，包括新生儿性别、出生体质量、出生孕周、出生地区，以及母亲年龄、胎数、户籍所在地。结果　本研究共收集到269 609例新生儿信息，男婴平均出生体质量（3 398±489）g，女婴平均出生体质量（3 294±471）g，低出生体质量儿10 753例（3.99%），巨大儿21 685例（8.04%）。不同性别、出生孕周、出生地区的新生儿低出生体质量、巨大儿发生率比较，差异均有统计学意义（P<0.05）。不同年龄、胎数、户籍所在地的母亲分娩的新生儿低出生体质量、巨大儿发生率比较，差异均有统计学意义（P<0.05）。多因素Logistic回归分析显示，女婴、早产儿、出生地区为城区，以及母亲年龄<25岁、多胎是低出生体质量儿发生的危险因素，男婴、过期产儿、出生地区为近郊和远郊，以及母亲年龄>34岁、单胎、非北京市户籍是巨大儿发生的危险因素（P<0.05）。结论　2014年北京市低出生体质量儿发生率较低，巨大儿发生率较高；新生儿性别、出生孕周、出生地区、母亲年龄和胎数是新生儿出生体质量异常的影响因素。

关键词: 婴儿, 出生时低体重, 巨大胎儿, 影响因素分析, 北京