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.