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.