Prevalence and factors associated with preterm small-for-gestational-age neonates: a multi-center survey in China

Small-for-gestational-age (SGA) infants represent major global health challenges, contributing significantly to neonatal mortality and long-term developmental morbidity. When compounded by preterm birth, the risks for adverse neonatal and long-term outcomes escalate dramatically. Research on preterm SGA neonates remains limited. This study aims to explore the prevalence and factors associated with preterm SGA neonates in China to break through the bottleneck of disease prevention and treatment.

A retrospective descriptive cross-sectional study was conducted in 23 provinces in China from 2011 to 2017. Detailed information on maternal characteristics, medical history was collected from medical records. The χ² test was used to compare the frequencies among categorical data and multinomial multivariate logistic regression was used to compare SGA preterm subgroups (< 32weeks, 32^+ 0~33^+ 6weeks, 34^+ 0~36^+ 6weeks) with appropriate-for-gestational-age(AGA) preterm group.

The prevalence of preterm SGA infants was 7.9%(1267/15734) in all singleton live-birth preterm infants. 159 preterm SGA infants at < 32weeks, 124 preterm SGA infants at 32 ~ 33weeks, 984 preterm SGA infants at 34 ~ 36weeks compared with 12,973 AGA infants. Hypertension disorders in pregnancy (HDP) and Category III fetal heart rate tracings were strongly associated with three preterm SGA subgroups. HDP was the strongest factor for preterm SGA at < 32weeks( aOR = 8.180, 95% CI 5.778 ~ 11.582). Category III fetal heart rate tracings was the factor with the highest OR value for preterm SGA at 32 ~ 33weeks (aOR = 4.785, 95% CI 3.049-7.508). Placental abruption was strongly associated with preterm SGA at < 32weeks (aOR = 7.073, 95% CI 3.102 ~ 16.127) and 32 ~ 33weeks(aOR = 6.055, 95% CI 2.309 ~ 15.878). Oligohydramnios(aOR = 6.526, 95% CI 2.309 ~ 16.887) was strongly associated with preterm SGA at 32 ~ 33weeks. GDM was a protective factor for preterm SGA at 34 ~ 36weeks(aOR = 0.516, 95% CI 0.343 ~ 0.778).

Different preterm SGA subgroups had different risk profiles. HDP and placenta abruption were more predictive of early preterm SGA. Category III fetal heart rate tracings and oligohydramnios were more predictive of moderate preterm SGA. GDM was a protective factor for late preterm SGA. Consequently, we underscore the importance of creating interventions that are tailored to particular gestational ages, rather than adopting a generalized approach, in order to effectively prevent preterm SGA outcomes.