Growth Trajectories in Infants From Families With Plant-Based or Omnivorous Dietary Patterns.

Importance: The safety of plant-based family diets, particularly vegan diets, during pregnancy and infancy is debated. Large population data on infant growth are scarce. Objective: To examine whether family dietary patterns (vegan, vegetarian, and omnivorous) are associated with growth trajectories, weight, and length among infants. Design, Setting, and Participants: This retrospective cohort study used data collected from January 1, 2014, through December 31, 2023, from a national network of public family care centers in Israel providing health and developmental surveillance for infants. Singleton births of infants gestational age 32 weeks or later without congenital malformations or birth weight less than 1500 g were followed up for 24 months. The data were analyzed between November 17, 2024, and December 6, 2025. Exposure: The family diet as recorded at least 6 months after delivery. Main Outcomes and Measures: The primary outcome was infant length. Secondary outcomes included weight, head circumference, stunting (length-for-age z score less than -2), underweight (weight-for-length z score less than -2), and overweight (weight-for-length z score >2). Growth trajectories were analyzed using linear mixed-effects models, and nutritional status at birth, early infancy (ie, first 60 days of life), and 24 months were analyzed using logistic regression. Results: Among 1 198 818 infants (mean [SD] gestational age, 39.2 [1.5] weeks; 53.2% male), 98.5% were from omnivorous households; 0.3% from vegan households, and 1.2% from vegetarian households. Differences in early-infancy length and length-for-age z scores among dietary groups were small (World Health Organization z score ≤0.3), and stunting prevalence was similar across groups (from 7.0% in the vegan and vegetarian groups to 7.1% in the omnivorous group), while underweight was more common in infants in the vegan vs omnivorous groups (adjusted odds ratio, 1.37 [95% CI, 1.15-1.63]). By age 24 months, stunting prevalence declined to 3.1%, 3.4%, and 3.9% in omnivore, vegetarian, and vegan groups, respectively, with no significant differences among the groups. Underweight and overweight were also low, with no differences by dietary group at age 24 months. Mean differences for weight, length, and head circumference were clinically minor (World Health Organization z score <0.2) and diminished further in adjusted longitudinal models. Conclusions and Relevance: In this cohort study, infants from vegan households had growth patterns similar to those from omnivorous households, with a higher odds of early underweight that decreased by age 24 months. In the context of developed countries, these findings seem reassuring. Further research should examine vegan diet quality and the impact of nutritional counseling during pregnancy and infancy in supporting optimal infant development.