Preconception Nutrition, Physical Activity, and Birth Outcomes in Adolescent Girls

Study Objective: Recommendations for preconception care usually include optimal nutrition and physical activity, but these have not been tested extensively for their relationship with birth outcomes such as low birth weight and preterm birth. Design: Data from Waves I, II, and IV of the National Longitudinal Study of Adolescent Health (Add Health) contractual dataset were used. Methods: In Wave I in-home interview, participants were asked to recall their frequency of having 5 types of food on the previous day, including milk, fruit, vegetables, grains, and sweets. At Wave II, participants reported the previous day's intake of 55 items, and results were categorized into high-calorie sweet, high-calorie nonsweet, and low-calorie food. At Wave I in-home interview, participants were also asked how many times in a week or during the past week they were involved in types of physical activity. At Wave IV, female participants reported pregnancies and birth outcomes. Multivariable linear regression analysis with survey weighting was used to predict birth weight and gestational age. Results: There were no associations between reported food intake and birth outcomes. Girls who engaged in more episodes of active behavior had higher birth weights (P < .01), but hours of sedentary behavior was not associated with birth weight. Multivariable analysis also indicated a U-shaped association between BMI and birth weight (P for quadratic term = .01). Conclusion: Adolescents who are more physically active before pregnancy have more positive birth outcomes as represented by birth weight.