目的 探究单胎活产小于胎龄儿（small for gestational age infant, SGA）的发生情况，并分析其高危因素。 方法 回顾性收集2019年1月—2024年1月山东第一医科大学附属人民医院1 020例单胎活产儿及其母亲的临床资料，统计SGA发生率，采用单因素和多因素logistic回归分析SGA的独立危险因素。 结果 1 020例单胎活产儿中SGA发生率为9.90%。新生儿为女性、胎盘重量较低或存在脐带异常者SGA发生率更高（均P<0.05）；早产、过期产与SGA发生率之间存在显著的线性趋势关系（均P<0.05）。母亲因素中，年龄<20岁或≥35岁、文化程度小学及以下、孕前低体重指数（body mass index, BMI）、孕期增重不足、妊娠高血压、糖尿病、贫血、甲状腺功能亢进、甲状腺功能减退、羊水/胎盘异常及孕母有吸烟史与新生儿更高的SGA发生率相关（均P<0.05）。多因素logistic回归分析显示，早产、过期产、低胎盘重量、脐带异常、孕前低BMI、孕期增重不足、妊娠高血压、妊娠期贫血、孕母有吸烟史是SGA发生的独立危险因素（均P<0.05）。 结论 单胎活产SGA的发生与早产、过期产、低胎盘重量、脐带异常、孕前低BMI、孕期增重不足、妊娠高血压、妊娠期贫血及吸烟史等危险因素相关，需针对性加强围产期管理以降低发生风险。

Objective To investigate the incidence of small for gestational age (SGA) infants among singleton live births and identify risk factors. Methods Clinical data for 1 020 singleton live-born infants and their mothers at People's Hospital Affiliated to Shandong First Medical University from January 2019 to January 2024 were retrospectively collected. The incidence of SGA was calculated, and univariate and multivariable logistic regression analyses were performed to determine independent risk factors. Results Among 1 020 singleton live births, the incidence of SGA was 9.90%. SGA was more frequent in female neonates and in cases with lower placental weight or umbilical cord abnormalities (all P<0.05). Both preterm and post-term birth showed significant linear trends with SGA incidence (P<0.05). Maternal factors associated with higher SGA incidence included age <20 years or ≥35 years, primary-school education or below, low pre-pregnancy body mass index (BMI), insufficient gestational weight gain, gestational hypertension, diabetes, anemia, hyperthyroidism, hypothyroidism, amniotic fluid/placental abnormalities, and smoking history (all P<0.05). Multivariable logistic regression identified preterm birth, post-term birth, low placental weight, umbilical cord abnormalities, low pre-pregnancy BMI, insufficient gestational weight gain, gestational hypertension, anemia during pregnancy, and maternal smoking as independent risk factors for SGA (all P<0.05). Conclusions The occurrence of SGA among singleton live births is associated with preterm or post-term delivery, low placental weight, umbilical cord abnormalities, low pre-pregnancy BMI, inadequate gestational weight gain, gestational hypertension, anemia during pregnancy, and maternal smoking. Targeted strengthening of perinatal management is warranted to reduce the risk of SGA.