Early physical growth and neurodevelopment in full-term small for gestational age infants: reference points from propensity score matching and restricted cubic splines

Introduction

Currently, small for gestational age (SGA) infants are defined as babies with a birth weight below the 10th percentile for their gestational age and sex in China. According to this standard, the incidence of SGA in China is approximately 6.4%, of which about 94% belong to full-term SGA (1). As a special group, full-term SGA has reached the standard of full-term delivery; however, due to reduced nutrient intake in the uterus and programmed changes in fetal metabolism (2), it exhibits different catch-up growth patterns and neurodevelopmental status after birth compared to the appropriate for gestational age (AGA) of full-term infants (3-5). At present, there is ongoing controversy regarding research on physical catch-up growth and neurodevelopment in full-term SGA. Studies have shown that full-term SGA has a higher risk of neurodevelopment than AGA (6), manifested not only by lower scores on the Bayley Scales of Infant Development (7,8) and the Brunet-Lézine Developmental Scale (9) during infancy and early childhood, but also by potential impacts on intellectual, academic, social, and psychological adaptation abilities in childhood, adolescence, and adulthood (10,11). However, some studies report that SGA status itself is not directly associated with neurodevelopmental outcomes. It is believed that postnatal growth (rather than whether birth weight matches gestational age) is the key factor determining later neurodevelopment (12,13). In fact, SGA children who achieve full catch-up growth often exhibit better neurodevelopmental outcomes (14,15). Adequate nutrition supply is crucial for brain development (16), and the weight gain that it brings is positively correlated with brain volume (17). The first months of life may represent an important period during which postnatal growth is associated with later developmental outcomes (13,18). The SGA International Consensus Guidelines for Children emphasize that clinical management during the first 2 years of life should focus on promoting catch-up growth through optimal nutritional support, while avoiding excessive early weight gain, as it is associated with long-term adverse health outcomes (19). A meta-analysis also showed a consistent positive association between weight gain and physical growth after full-term SGA birth, as well as with neurodevelopmental outcomes, obesity, insulin resistance, and blood pressure (20). Therefore, finding a balance between promoting neurodevelopment and preventing metabolic risks, while establishing a suitable catch-up growth pattern, remains an important practical issue in pediatric follow-up (21). To address this, we conducted a cross-sectional study systematically analyzing the correlation between physical growth, birth factors, and neurodevelopment at 1 year of age in full-term SGA and AGA infants. Our objectives were fourfold: to identify factors associated with neurodevelopment in full-term SGA and AGA infants; to explore heterogeneity within the SGA group by age- and sex-adjusted relative length at 1 year; to assess whether SGA status remained associated with developmental quotient (DQ) scores after accounting for measured covariates; and to estimate model-derived weight-ratio reference points corresponding to the average DQ levels of AGA infants. We present this article in accordance with the STROBE reporting checklist (available at https://tp.amegroups.com/article/view/10.21037/tp-2026-0266/rc).

Methods

Study design and participants

This cross-sectional study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of The Second Affiliated Hospital of Army Medical University (Approval No. 2025; Research No. 338-01),and the requirement for informed consent was waived because of the retrospective nature of the study. Data were retrospectively collected from full-term SGA and AGA infants who attended the Child Health Clinic at our institution between November 2019 and July 2025.

The inclusion criteria were a gestational age of 37‒42 weeks and birth weight below the 10th percentile for sex and gestational age for the SGA group, based on Chinese national standards (22). The AGA group included infants with birth weights between the 10th and 90th percentiles. The exclusion criteria for both groups were a diagnosis of brain injury, epilepsy, visual or hearing impairment, congenital heart disease, or confirmed chromosomal or inherited metabolic disorders (excluding heterozygous thalassemia).

Data collection

At the 1-year follow-up visit, trained child healthcare staff measured weight, length, and head circumference. Neurodevelopment was assessed using the Gesell Developmental Scale (GDS) by certified evaluators. The GDS assesses five domains: gross motor, fine motor, adaptive behavior, language, and personal-social behavior. The DQ for each domain was calculated as follows: DQ = (developmental age/chronological age) × 100.

Statistical analysis

Statistical analyses were performed using Stata version 17.0. Continuous variables with non-normal distributions are presented as medians and interquartile ranges (IQRs) and were compared using the Mann-Whitney U test. Categorical variables are expressed as counts and percentages and were compared using the Pearson χ² test.

To identify factors associated with neurodevelopment, separate generalized linear models (GLMs) with a gamma distribution and a log link were constructed for the SGA and AGA groups. The independent variables included sex, birth weight, gestational age, mode of delivery, and anthropometric measurements at age 1 year (weight, length, and head circumference).

To further examine heterogeneity within the SGA group, we derived an age- and sex-adjusted relative length indicator at 1 year. Relative length was defined as the observed 1-year length divided by the predicted length from a reference model fitted in the AGA group using sex and assessment age. SGA infants were then stratified into low, middle, and high relative-length groups using the 25th and 75th percentiles of this ratio.

As an exploratory analysis, SGA infants were additionally stratified by sex-specific weight status at 1 year using the 25th percentile of the reference standard (23) as a pragmatic cut point (<P25 vs. ≥P25). This grouping was used for descriptive comparison and was not intended as a biological definition of catch-up success or failure.

To assess whether SGA status remained associated with neurodevelopment after accounting for measured covariates, we applied a two-step propensity score matching (PSM) approach. First, 1:1 nearest-neighbor matching (PSM1) was performed using sex, mode of delivery, gestational age, and assessment age as covariates. Second, a 1:2 matching (PSM2) was additionally performed, incorporating weight, length, and head circumference at age 1 year. Covariate balance was evaluated using absolute standardized mean differences, with values around or below 10% considered indicative of acceptable balance. After each matching step, weighted GLMs were used to estimate the effect of SGA status on DQ in each domain.

To further characterize the quantitative relationship between the 1-year weight ratio and neurodevelopment in SGA infants, restricted cubic spline (RCS) models were employed. The weight ratio was defined as the 1-year weight of an SGA infant divided by the average weight of sex-matched AGA infants. The model-derived weight ratio at which the predicted mean DQ was closest to the average DQ of the AGA group was defined as a reference point for developmental comparison. All tests were two-sided, and statistical significance was set at P<0.05.

Results

Study population characteristics before matching

A total of 2,824 children were included, comprising 448 full-term SGA and 2,376 full-term AGA infants. Before matching, the SGA group had a significantly lower median birth weight (2.68 vs. 3.30 kg, P<0.001) and a higher proportion of females (57.81% vs. 46.76%, P<0.001). Gestational age and mode of delivery did not differ significantly between the two groups (P=0.15). At age 1 year, SGA infants remained significantly smaller than AGA infants in terms of weight, length, and head circumference (all P<0.001). Despite these anthropometric differences, no statistically significant differences in DQ scores across any of the five GDS domains were observed between the two groups before matching (P=0.60, P=0.75, P=0.36, P=0.93, P=0.78). The baseline characteristics are presented in Table 1.

Factors associated with neurodevelopment in full-term SGA and AGA groups

GLM analyses revealed distinct patterns of factors associated with neurodevelopment between the two groups (Tables 2,3).

In the full-term SGA group (n=448), body weight at 1 year was the most prominent factor, showing strong positive associations with DQ in multiple domains (fine motor, adaptive behavior, language, and personal-social) (P=0.008, P<0.001, P<0.001, P<0.001). Additionally, body length was positively associated with gross motor DQ (P=0.003), and vaginal delivery was associated with better outcomes in gross motor, language, and personal-social behavior domains compared with cesarean section (P=0.007, P=0.04, P=0.01). Females had higher DQ in the adaptive behavior, language, and personal-social domains (P=0.002, P<0.001, P=0.001), whereas birth weight was negatively correlated with gross motor DQ (P=0.01).

In contrast, in the full-term AGA group (n=2,376), longer gestational age was the factor most consistently associated with higher DQ across the gross motor, fine motor, adaptive behavior, and personal-social behavior domains (P=0.02, P=0.02, P=0.009, P=0.006). Birth weight was positively associated with fine motor and personal-social DQ (P=0.005, P=0.04). Head circumference at 1 year was positively correlated with fine motor and personal-social behavior DQ (both P<0.001), and 1-year-old body length was positively correlated with gross motor DQ (P=0.01). Unlike in the SGA group, there was a negative correlation (β=−0.7%, P=0.02) between 1-year body weight and gross motor DQ in the AGA group. Female sex also showed advantages in multiple domains (fine motor, adaptive behavior, language, and personal-social behavior) (P=0.03, P=0.004, P<0.001, P<0.001), and vaginal delivery was positively correlated with adaptive behavior DQ (P=0.04).

Heterogeneity of full-term SGA infants stratified by relative length at 1 year

To further examine heterogeneity within the full-term SGA group, we stratified SGA infants according to age- and sex-adjusted relative length at 1 year. Relative length was defined as the observed 1-year length divided by the predicted length derived from the AGA reference model adjusted for sex and assessment age. Using the 25th and 75th percentiles of this ratio, SGA infants were classified into low (n=112), middle (n=224), and high (n=112) relative-length strata (Table 4).

Gestational age and assessment age did not differ significantly across the three strata (P=0.28 and P=0.62, respectively), and the sex distribution was also comparable (P=0.64). In contrast, birth weight differed significantly across strata (P=0.003), with the low relative-length group showing the lowest median birth weight. Delivery mode also differed significantly (P=0.004), with a lower proportion of vaginal delivery in the low relative-length group.

At age 1 year, anthropometric measures showed clear gradients across the three strata. Median body weight increased from 8.10 kg in the low relative-length group to 8.90 kg in the middle group and 9.60 kg in the high group (P<0.001). Median body length increased from 70.50 to 73.45 and 76.00 cm (P<0.001), and median head circumference increased from 44.25 to 44.80 and 45.35 cm (P<0.001).

Neurodevelopmental performance improved progressively with increasing relative length. Median gross motor DQ increased from 84 to 86 and 89 (P<0.001), fine motor DQ from 87 to 88 and 89 (P=0.002), adaptive behavior DQ from 86 to 87 and 88 (P<0.001), language DQ from 77 to 79 and 83 (P<0.001), and personal-social DQ from 84 to 85 and 87 (P<0.001). Overall, these findings indicate substantial heterogeneity within the full-term SGA population and show that poorer linear growth status at 1 year is accompanied by less favorable anthropometric and neurodevelopmental profiles.

Exploratory comparison by weight status at 1 year in full-term SGA infants

As an exploratory analysis, full-term SGA infants were additionally stratified by sex-specific weight status at 1 year using the 25th percentile as a pragmatic cut point (<P25 vs. ≥P25). The two groups did not differ significantly in birth characteristics, including birth weight, gestational age, and mode of delivery (P=0.98, P=0.68, P=0.28). However, infants in the higher weight-status group had greater weight, length, and head circumference at 1 year than those in the lower weight-status group (all P<0.001). They also had higher DQ scores across all five GDS domains (in the female SGA group, P=0.004 for the fine motor domain and P<0.001 for all other domains; in the male SGA group, P<0.001 for all domains) (Table 5). This analysis should be interpreted as a descriptive subgroup comparison based on weight status at 1 year rather than as a biological classification of catch-up growth.

Evaluation of the association of full-term SGA status with neurodevelopment after matching

To examine whether full-term SGA status remained associated with neurodevelopment after accounting for measured covariates, we performed a two-step PSM analysis. In PSM1, sex, mode of delivery, gestational age, and assessment age were included as matching covariates. After matching, 991 children were retained, including 448 SGA and 543 AGA infants. Covariate balance improved substantially after matching, with all post-matching absolute standardized mean differences approximately ≤10% (Table S1 and Figure S1). Weighted GLM analysis showed no statistically significant differences in DQ scores between the SGA and AGA groups across any of the five GDS domains (P=0.27, P=0.80, P=0.26, P=0.60, P=0.83).

In PSM2, weight, length, and head circumference at 1 year were additionally incorporated into the matching procedure. After matching, 1,082 children were retained, including 448 SGA and 634 AGA infants. Covariate balance was further improved, with all post-matching absolute standardized mean differences <4% (Table S1, Figure S1). Similarly, no statistically significant between-group differences in DQ scores were detected in any domain after matching (P=0.80, P=0.86, P=0.97, P=0.64, P=0.71) (Table 6). These findings indicate that, within this dataset and after matching on the measured covariates, full-term SGA status was not significantly associated with 1-year neurodevelopmental scores.

Weight ratio reference points for neurodevelopmental comparison in full-term SGA infants

RCS models were used to characterize nonlinear associations between the 1-year weight ratio and DQ scores across the five GDS domains. Significant nonlinear associations were observed in all domains (all P<0.001). The model-derived weight-ratio reference points at which the predicted mean DQ was closest to the corresponding average AGA DQ are shown in Table 7 and Figure 1.

Figure 1 RCS analyses of the associations between the 1-year weight ratio and DQ scores among full-term SGA infants. Panels show the gross motor (A), fine motor (B), adaptive behavior (C), language (D), and personal-social (E) domains. Gray dots represent observed SGA infants, and short gray rug marks near the bottom of each panel indicate the distribution of observed weight-ratio values. The blue line represents the RCS-fitted association between weight ratio and DQ, and the light blue vertical band indicates the corresponding 95% confidence interval. The maroon dashed horizontal line indicates the mean DQ of the AGA group in the corresponding domain. The green dashed vertical line marks the model-derived reference point at which the predicted mean DQ of SGA infants was closest to the average DQ of the AGA group. In (E), two green dashed vertical lines are shown because the fitted curve crossed the AGA mean DQ line at two points; the right-sided crossing is additionally displayed for completeness. AGA, appropriate for gestational age; DQ, developmental quotient; SGA, small for gestational age; RCS, restricted cubic spline.

For gross motor, fine motor, adaptive behavior, and language, the fitted curves generally increased with increasing weight ratio. The corresponding reference points were 0.901 for gross motor, 0.909 for fine motor, 0.864 for adaptive behavior, and 0.890 for language (Figure 1A-1D). The personal-social domain showed a U-shaped pattern; because the fitted curve crossed the AGA mean line twice, both crossings are displayed in Figure 1E, while the lower crossing point (0.741) was used as the primary reference point in Table 7.

Discussion

This study examined the cross-sectional associations between early physical growth and 1-year neurodevelopmental scores in full-term SGA infants and compared these patterns with those observed in full-term AGA infants. Several findings merit emphasis. First, within the SGA group, body weight at 1 year showed positive associations with DQ scores across multiple developmental domains. Second, stratification by age- and sex-adjusted relative length at 1 year revealed substantial heterogeneity within the SGA population, with infants in the lower relative-length stratum showing less favorable anthropometric and neurodevelopmental profiles. Third, after matching on the measured covariates, we did not observe statistically significant differences in 1-year DQ scores between the SGA and AGA groups. Lastly, RCS analyses identified model-derived weight-ratio reference points corresponding to average AGA developmental levels, although these values should be interpreted cautiously rather than as causal or universal clinical thresholds.

Distinct growth-development association patterns in full-term SGA and AGA infants

Our multivariable analyses showed different association patterns in the SGA and AGA groups. Among full-term SGA infants, body weight at 1 year was the factor most consistently associated with higher DQ scores, particularly in the fine motor, adaptive behavior, language, and personal-social domains. Body length at 1 year was additionally associated with gross motor DQ. Together, these findings suggest that, within the SGA group, postnatal growth status was closely linked to concurrent developmental performance at 1 year. This pattern is consistent with previous work (14,18) indicating that postnatal growth may be an important correlate of neurodevelopment among infants born with early growth disadvantage. In contrast, among full-term AGA infants, gestational age and birth weight showed broader associations across several domains, whereas the associations of postnatal anthropometric indicators were more limited and domain-specific. A study by Beyerlein et al. (24) also reported no positive correlation between rapid weight gain and intelligence scores in non-SGA children. This difference between groups suggests that the relative contribution of birth-related versus postnatal growth-related factors may not be the same in SGA and AGA children. Rather than implying causation, our findings indicate that developmental scores at 1 year in full-term SGA infants may be more closely aligned with postnatal anthropometric status, whereas in AGA infants, variation in developmental scores may be associated more strongly with baseline perinatal characteristics.

Heterogeneity within full-term SGA infants revealed by relative length at 1 year

An important finding of this study is that full-term SGA infants were not a homogeneous group. Previous research has indicated that stunting is the most prevalent form of childhood undernutrition (25). When the SGA group was stratified according to age- and sex-adjusted relative length at 1 year, infants in the lower relative-length stratum had lower body weight, shorter length, smaller head circumference, and lower DQ scores across all five GDS domains than those in the higher relative-length stratum. In contrast, gestational age, assessment age, and sex distribution did not differ significantly across strata. These results suggest that linear growth status at 1 year provides additional information for describing heterogeneity within the SGA population beyond birth-size classification alone.

This finding is clinically relevant because SGA is a statistical birth-size category rather than a biologically uniform condition. Some infants classified as SGA may have experienced true fetal growth restriction, whereas others may be constitutionally small. Our relative-length stratification does not resolve these etiologic differences, but shows that postnatal linear growth status is closely accompanied by differences in both anthropometric and developmental profiles. In this sense, length-based subgrouping offers a useful descriptive approach for characterizing variation within term SGA infants and complements the weight-related findings of our multivariable models.

No significant between-group difference in 1-year DQ scores after matching measured covariates

After matching the measured covariates, we did not observe statistically significant differences in 1-year DQ scores between the full-term SGA and AGA groups. This finding suggests that, within this retrospective clinic-based dataset, SGA status was not significantly associated with developmental scores once the available birth-related and postnatal growth-related variables were considered. Importantly, this result should not be interpreted as evidence that SGA status has no developmental relevance in all settings, nor does it negate prior studies reporting poorer outcomes in children born SGA (6-11). Rather, it indicates that in our sample, postnatal anthropometric status showed stronger cross-sectional associations with DQ than birth-size category after adjustment for the measured variables, with some studies reporting similar findings (14,15,26).

This interpretation should be made cautiously. Our matching procedure could account only for the variables available in the dataset and could not address potentially important unmeasured factors such as parental education, socioeconomic conditions, maternal health complications, or detailed feeding and nutritional exposures. In addition, developmental assessment at 1 year has limited ability to predict later cognitive or behavioral outcomes. Therefore, the PSM findings are best viewed as conditional on the measured covariates available in this study rather than as a definitive statement that term SGA status is unrelated to later neurodevelopment.

Model-derived weight-ratio reference points and their cautious interpretation

Previous work suggests that weight gain may be more pronounced than gains in length or head circumference in term SGA children younger than 2 years (27), indicating that body weight may be a more sensitive monitoring indicator in this age group. In our multivariable analyses, weight at 1 year showed the most consistent associations with DQ across domains in the SGA group, further supporting the importance of monitoring weight during early follow-up. In addition to the multivariable analyses, the RCS models showed significant nonlinear associations between the 1-year weight ratio and DQ scores across all five GDS domains. For gross motor, fine motor, adaptive behavior, and language, the fitted curves generally increased as the weight ratio increased, although the estimated reference points at which predicted mean DQ approached the average AGA level differed by domain. The corresponding values were highest for the gross motor, fine motor, and language domains (0.901, 0.909, and 0.890, respectively), followed by the adaptive behavior domain (0.864). In contrast, the personal-social domain displayed a U-shaped pattern, with the lower crossing point at 0.741, indicating that the association between relative weight status and this domain may be more complex than a simple monotonic relationship.

This heterogeneity likely reflects differences in the neurobiological substrates and developmental timetables of specific cognitive functions. Brain development follows a nonlinear trajectory, with different regions maturing at different ages (28); moreover, the timing and nutritional demands of the neural substrates underlying various cognitive domains are not uniform (29). The higher reference values observed for motor and language domains might reflect greater sensitivity to nutritional status during critical periods of regional brain maturation, although this interpretation remains speculative.

Nevertheless, these spline-derived values should be interpreted cautiously. They represent model-based reference points within this retrospective cross-sectional dataset, not causal thresholds and not universal clinical targets. In particular, they do not demonstrate that increasing an individual infant’s weight to a given ratio will necessarily improve neurodevelopmental outcomes, nor do they account for unmeasured influences such as maternal health, family environment, socioeconomic conditions, or detailed nutritional exposures. The U-shaped pattern observed for personal-social DQ is also difficult to interpret mechanistically in a cross-sectional setting and should be regarded as a descriptive finding that warrants further study rather than as evidence of a specific developmental adaptation. Overall, the spline analysis is best viewed as a way to characterize nonlinear growth-development patterns and generate hypotheses for future longitudinal research.

Other associated factors

In addition to the anthropometric variables, female sex and vaginal delivery were associated with more favorable DQ scores in several domains. These findings are broadly consistent with previous studies reporting sex-related differences in early neurodevelopment (28,30,31) and possible associations between delivery mode and developmental outcomes (32,33). However, these associations should also be interpreted cautiously. They may reflect a combination of biological differences, perinatal conditions, and unmeasured family or environmental influences rather than isolated effects of sex or delivery mode alone. Although these variables were not the primary focus of the present study, they may help identify subgroups of infants who warrant closer developmental follow-up.

Strengths, limitations, and future directions

This study has several strengths. It included a relatively large sample of full-term SGA and AGA infants from routine child health follow-up, examined developmental domains separately rather than relying on a single composite outcome, and applied multiple complementary analytical approaches, including multivariable modeling, PSM, subgroup analysis by relative length, and RCS modeling. In particular, the additional length-based heterogeneity analysis provided a useful descriptive perspective on variation within the SGA group.

Several limitations should be acknowledged. First, this was a single-center retrospective cross-sectional study, which limits generalizability and precludes causal inference. Second, developmental assessment was performed only at approximately age 1 year, and developmental scores at this age have limited ability to predict later cognitive, behavioral, or academic outcomes. Third, SGA was defined by birth weight percentile and should not be assumed to be synonymous with fetal growth restriction; constitutionally small infants may have been included in the SGA group. Fourth, although we adjusted or matched for several measured variables, important potential confounders were unavailable, including parental education, socioeconomic status, maternal health conditions such as hypertensive disorders, and detailed feeding or nutritional intake data. Residual confounding is therefore likely. Fifth, the spline-derived weight-ratio values are statistical reference points within this dataset and should not be interpreted as treatment thresholds or universal intervention targets.

Future studies should use multicenter longitudinal designs to evaluate how growth trajectories in weight, length, and head circumference relate to neurodevelopment from infancy through later childhood. Incorporating more detailed maternal, family, and nutritional data would help clarify the extent to which observed associations reflect biological vulnerability, postnatal growth patterns, or broader social determinants of health. Studies using repeated developmental assessments, body composition measures, and, where feasible, neuroimaging or other biological markers may further improve understanding of the mechanisms linking early growth and neurodevelopment in full-term SGA infants.

Conclusions

In this retrospective cross-sectional study, 1-year neurodevelopmental scores in full-term SGA infants were more closely associated with postnatal growth status than with SGA status after matching the measured covariates. In the SGA group, body weight at 1 year was positively associated with DQ scores across multiple domains, whereas in the AGA group, perinatal factors showed broader associations. Age- and sex-adjusted relative length at 1 year further demonstrated substantial heterogeneity within the SGA group. This study also identified model-derived weight-ratio reference points at which predicted mean DQ in SGA infants approximated the average DQ levels of AGA infants across different domains. These values may be useful for developmental comparison and follow-up assessment; however, they should not be interpreted as causal thresholds or universal clinical targets. Given the single-center retrospective design and the limitation of developmental assessment at age 1 year, the findings should be interpreted cautiously.

Acknowledgments

We thank Bin Hu at Chongqing University Press (Medical Branch) for his insightful comments and suggestions on the manuscript. We would like to thank Editage (www.editage.cn) for English-language editing.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tp.amegroups.com/article/view/10.21037/tp-2026-0266/rc

Data Sharing Statement: Available at https://tp.amegroups.com/article/view/10.21037/tp-2026-0266/dss

Peer Review File: Available at https://tp.amegroups.com/article/view/10.21037/tp-2026-0266/prf

Funding: This study was funded by the Ministry of Science and Technology of the People’s Republic of China’s Science and Technology Innovation 2030 initiative under the Major Project of “Brain Science and Brain-like Research” (No. 2021ZD0201700).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tp.amegroups.com/article/view/10.21037/tp-2026-0266/coif). Yuping Zhang reports the funding from the Ministry of Science and Technology of the People’s Republic of China’s Science and Technology Innovation 2030 initiative under the Major Project of “Brain Science and Brain-like Research” (No. 2021ZD0201700). The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of The Second Affiliated Hospital of Army Medical University (Approval No. 2025; Research No. 338-01), and the requirement for informed consent was waived because of its retrospective nature.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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