Gestational age-standardized neonatal growth patterns in adolescent pregnancy.

OBJECTIVE: To evaluate whether differences in neonatal size in adolescent pregnancy reflect prematurity or intrinsic fetal growth restriction using gestational age-adjusted growth metrics. STUDY DESIGN: This retrospective single-center study included 329 mother-infant dyads (111 adolescents ≤19 years; 218 adults aged 20-35 years). Neonatal anthropometric measurements were converted into sex- and gestational age-adjusted z-scores using INTERGROWTH-21st standards. Birth weight, length, and head circumference z-scores, along with ponderal index, and growth asymmetry (HC_z - BW_z) were compared between groups. Multivariable regression analyses adjusted for gestational age, maternal smoking, neonatal sex, and maternal hemoglobin level. RESULTS: In unadjusted analyses, infants born to adolescents had lower birth weight, length, and head circumference (all p < 0.001). After gestational age standardization, no statistically significant differences were detected in birth weight or length z-scores. A small nominal difference was observed in head-circumference z-score (Cohen's d = -0.25; nominal p = 0.031), which should be interpreted cautiously. Ponderal index and growth asymmetry did not differ. In multivariable analyses, adolescent pregnancy was not independently associated with birth weight or length z-scores but showed a modest association with lower head-circumference z-score (β = -0.35, 95% CI -0.61 to -0.08). Adolescent pregnancy remained independently associated with preterm birth (adjusted OR 2.39), while its association with low birth weight was attenuated. CONCLUSION: Adverse neonatal outcomes in adolescent pregnancy appear to be largely mediated through prematurity rather than generalized impairment in fetal growth. A modest difference in head-circumference z-score was observed, but its clinical relevance remains uncertain and requires confirmation in larger prospective studies. Gestational age-standardized assessment may improve the interpretation of neonatal growth patterns in adolescent pregnancy.