Risky Health Behaviors of Teenage Mothers and Infant Outcomes in the Japan Environment and Children's Study: A Nationwide Cohort Study

Study Objective: Few studies have investigated the risky health behaviors and psychosocial characteristics of teenage mothers in countries with a low teenage birth rate, like Japan. We examined the differences in maternal prenatal risky health behaviors and psychosocial characteristics, and birth weight of infants between teenage and adult mothers. Design, Setting, Participants, Interventions, and Main Outcome Measures: We identified 1159 teenage (age younger than 20 years) and 73,547 adult mothers (20-34 years) who participated a nationwide birth cohort study between 2011 and 2014. Behavioral and psychosocial characteristics were ascertained using questionnaires during pregnancy. Birth weight of infants was verified through medical records. Univariate and multivariable logistic regression were used to assess the association of teenage motherhood and birth weight of infants with parity, marital status, household income, maternal education, job status, preconception body mass index, gestational weight gain, psychological distress, and smoking status. Results: Teenage mothers were significantly more likely to smoke and have psychological distress and less likely to use alcohol than adult mothers (9.9% vs 4.6%, P < .001; 8.9% vs 3.4%, P < .001; 1.3% vs 2.5%, P < .001, respectively). No association was found between teenage motherhood and low birth weight in infants (odds ratio 0.99; 95% confidence interval, 0.73-1.32). Further, no association was found after adjusting for covariates. Conclusion: A substantially greater number of Japanese teenage mothers smoked and experienced severe psychological distress than adult mothers. Our findings will be useful for future research and for developing effective policies and programs for teenage mothers and their children.