# Cord Blood Mitochondrial DNA Copy Number and Physical Growth in Infancy and Toddlerhood: A Birth Cohort Analysis

## TL;DR

This study explores whether mitochondrial DNA copy number in cord blood is linked to physical growth in early childhood, but finds no significant associations.

## Contribution

The study provides a foundation for future research on cord blood mtDNAcn and early-life growth.

## Key findings

- Cord blood mtDNAcn showed no significant associations with body weight or height up to 48 months.
- Growth trajectories of infants with higher or lower mtDNAcn converged toward the population mean.

## Abstract

Background/Objectives: Cord blood mitochondrial DNA copy number (mtDNAcn) has been proposed as a biomarker reflecting environmental influences during fetal life, with reported associations with perinatal outcomes such as birth weight and length. Within the framework of the Developmental Origins of Health and Disease (DOHaD) theory, this study aimed to investigate whether cord blood mtDNAcn is related to postnatal physical growth in early childhood. Methods: We analyzed data from 150 newborns (68 females and 82 males) enrolled in the Tohoku Medical Megabank Birth and Three-Generation Cohort Study in Japan. Cord blood mtDNAcn was quantified using real-time PCR, and standard deviation scores for weight and height were assessed at 1, 2–3, 4–6, 18–24, and 36–48 months of age. Correlation analyses were conducted separately by sex. Results: Cord blood mtDNAcn showed no significant associations with body weight or height at any of the postnatal time points up to 48 months of age. Growth trajectories of infants with higher or lower mtDNAcn values at birth tended to converge toward the population mean during infancy and toddlerhood. Conclusions: Although no significant relationships were observed, this exploratory, hypothesis-generating study provides a foundation for future investigations. Larger cohorts with extended follow-up are needed to clarify the potential significance of cord blood mtDNAcn in early-life research on child growth and health.