Trajectories of Weight for Length Growth for Infants During the First Year of Life

Abstract

Background: Childhood obesity is a major public health problem. Studies of patterns of child growth contributing to the development of obesity are scarce, particularly in infancy. Group based trajectory analyses among infants are a novel procedure that may help characterize subgroups of infants with similar longitudinal growth profiles. Objective: To identify trajectories of weight for length growth during the first year of life. Methods: Subjects were singleton infants and their mothers (N=90 mother-infant pairs) who participated in the Pregnancy and Postpartum Observational Dietary Study. Women completed assessments throughout their infant's first year of life and included sociodemographic characteristics and feeding behaviors. Infant weight for length measures from birth to 12 months were abstracted from pediatric office records. Weight for length percentiles were calculated according to the World Health Organization guidelines for infants. Group-based trajectory analysis was done to identify subgroups of infants with similar growth profiles. Results: Infants were from mother’s with average of 28 years (SD=5.2), 70.0% White, 60.0% high-school educated and 63.2% had two or more children. Over half of mothers introduced solid foods to their infants by 6 months of age (63.2%) and about one third self-reported breast feeding at 12 months post-partum (31.9%). Three growth trajectories were identified: a low and stable growth group (38.3%), a rapid growth group (35.0%) and a moderate growth group (26.7%). Maternal and feeding variables were all similar across the three infant growth trajectory groups (p>0.05). Conclusion: Trajectory models suggested three patterns of infant growth. If replicated, future studies can help identify and subsequently target modifiable risk factors associated with rapid infant growth trajectories.