Objective To investigate the correlation between the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and C-reactive protein (CRP) in the serum of full-term small-for-date infants and their growth restriction.

Methods Pregnant women and their newborns who underwent routine check-ups at the Department of Obstetrics of Xingtai Central Hospital were enrolled. The mothers were admitted for delivery between January 2022 and December 2023. Newborns with a gestational age between 37 weeks and 41 weeks 6 days were included. A total of 83 newborns weighing < 2500 g at birth were included in the full-term small-for-date infant group, while 72 newborns weighing ≥ 2500 g at birth were included in the healthy control group. The maternal and neonatal serum levels of TNF-α, IL-6, and CPR were compared between the two groups. Logistic regression analysis was performed to screen for influencing factors. Receiver operating characteristic (ROC) curves were plotted to assess the predictive value of each influencing factor, and the optimal cutoff value, sensitivity, and specificity were derived subsequently.

Results Compared with the healthy group, the full-term small-for-date infant group had elevated maternal and neonate serum levels of TNF-α, IL-6, and CPR (P < 0.001). Maternal body mass index (BMI) (OR = 0.428; 95% CI, 0.238-0.768; P = 0.004), TNF-α levels (OR = 2.133; 95% CI, 1.012-4.496; P = 0.046), IL-6 levels (OR = 1.218; 95% CI, 1.121-1.322; P < 0.001), and CPR levels (OR = 1.733; 95% CI, 1.312-2.288; P < 0.001) were significantly associated with the incidence of full-term small-for-date infants (P < 0.05). The area under the ROC curve (AUC) for maternal BMI and maternal serum TNF-α, IL-6, and CPR levels were 0.358 (0.271-0.444), 0.735 (0.656-0.814), 0.838 (0.777-0.898), and 0.743 (0.666-0.820), respectively. Among the 83 cases of full-term small-for-date infants, 49 cases (59.04%) achieved satisfactory weight according to infant weight evaluation standards by the age of 6 months. Only birth weight (OR = 1.004; 95% CI, 1.312-2.288; P < 0.001) was identified as a significant influencing factor for satisfactory catch-up growth in full-term small-for-date infants. There was no significant association between the levels of inflammatory cytokines at birth and satisfactory catch-up growth at 6 months of age.

Conclusion Maternal BMI and maternal and neonatal serum levels of TNF-α, IL-6, and CPR are all associated with the occurrence of growth restriction in full-term small-for-date infants. Measuring maternal serum levels of TNF-α, IL-6, and CPR may have value in predicting the occurrence of full-term small-for-date infants. However, no significant correlation is identified between the neonate serum levels of TNF-α, IL-6, and CRP and their growth catch-up at 6 months of age.