[Factors influencing the occurrence of small for gestational age at different degrees].

Objectives: To investigate the factors influencing the occurrence of small for gestational age (SGA) at different degrees and provide a basis for early identification of severe SGA cases.
Methods: Neonatal and maternal prenatal information were retrospectively collected from January 2018 to December 2022 at Peking University People's Hospital. The neonates were divided into three groups: severe SGA group (birth weight below the 3rd percentile for gestational age and sex), mild SGA group (birth weight ≥3rd percentile and <10th percentile), and non-SGA group (birth weight ≥10th percentile). An ordered multinomial logistic regression model was used to analyze the factors influencing the occurrence of SGA at different degrees.
Results: A total of 14 821 neonates were included, including 258 cases (1.74%) in the severe SGA group, 902 cases (6.09%) in the mild SGA group, and 13 661 cases (92.17%) in the non-SGA group. The proportions of preterm births and stillbirths were higher in the severe SGA group compared to the mild SGA and non-SGA groups ( P <0.0125). The proportion of neonatal asphyxia was higher in both the severe SGA and mild SGA groups compared to the non-SGA group ( P <0.0125). Ordered multinomial logistic regression analysis showed that maternal pre-pregnancy underweight ( OR =1.838), maternal pre-pregnancy obesity ( OR =3.024), in vitro fertilization-embryo transfer ( OR =2.649), preeclampsia ( OR =1.743), connective tissue disease during pregnancy ( OR =1.795), nuchal cord ( OR =1.213), oligohydramnios ( OR =1.848), and intrauterine growth restriction ( OR =27.691) were all associated with a higher risk of severe SGA ( P <0.05). Maternal parity as a multipara ( OR =0.457) was associated with a lower likelihood of severe SGA ( P <0.05).
Conclusions: Maternal pre-pregnancy underweight, maternal pre-pregnancy obesity, in vitro fertilization-embryo transfer, preeclampsia, connective tissue disease during pregnancy, oligohydramnios, nuchal cord, and intrauterine growth restriction are closely related to the occurrence of more severe SGA. Maternal parity as a multipara acts as a protective factor against the occurrence of severe SGA.