Perinatal Outcomes of Pregnant Adolescents in Rural Japan: A Retrospective Cohort Study at a Comprehensive Perinatal Center

Background Globally, even within developed nations, specific regions exhibit disproportionately high rates of adolescent pregnancy that require comprehensive perinatal medical care, including social interventions. We aimed to compare perinatal outcomes between pregnant adolescents and pregnant adults in rural Japan. Methods We conducted a retrospective cohort study of pregnant women between 2014 and 2025, categorizing participants into two groups based on maternal age: pregnant adolescents (< 20 years) and adults (20–34 years). Adjusted odds ratios (aORs) were calculated using logistic regression analysis. Results Of the 3157 singleton pregnant women identified, 142 (4.5%) were adolescents and 3015 (95.5%) were adults. Adolescent pregnancy was significantly associated with nulliparity (p < .001), shorter stature (p < .001), lower pre-pregnancy body weight (p < .001), lower body weight at delivery (p < .001), and lower pre-pregnancy body mass index (p = .0065). Adolescents were also more likely to smoke during pregnancy (p = .041), and to undergo pregnancy termination before 22 weeks of gestation (p < .001). Multivariable analysis revealed that the adolescent group had significantly higher risks for fetal growth restriction (aOR, 1.82; 95% confidence interval [CI], 1.00–3.30), preterm delivery (aOR, 1.86; 95% CI, 1.02–3.37), low birth weight (aOR, 1.51; 95% CI, 1.04–2.19), low Apgar score at 5 minutes (aOR, 4.21; 95% CI, 2.09–8.48), and admission to the neonatal intensive care unit (aOR, 1.46; 95% CI, 1.02–2.08). Conversely, the incidences of gestational diabetes mellitus (aOR, 0.18; 95% CI, 0.0057–0.57), and cesarean delivery (aOR, 0.48; 95% CI, 0.33–0.69) were significantly lower in the adolescent group than those in the adult group. Conclusion We found that adolescent pregnancy in rural Japan was associated with important adverse perinatal outcomes, including preterm delivery, low birth weight, low Apgar scores at 5 minutes, and neonatal intensive care unit admission. The present findings underscore the importance of providing targeted perinatal support and specialized obstetric care for pregnant adolescents to mitigate these risks.