# Association between fetal eye movement density and developmental problems at age 3 years

## TL;DR

Higher fetal eye movement density at 34-36 weeks is linked to better language development and lower risk of repetitive behaviors at age 3.

## Contribution

This study identifies fetal eye movement density as a potential early biomarker for developmental and behavioral risks.

## Key findings

- Higher fetal EMD correlates with better receptive and expressive language at age 3.
- Lower EMD is associated with higher restricted and repetitive behavior scores.
- Lower EMD predicts later bedtimes at 1 year of age.

## Abstract

In this longitudinal study of 77 pregnant women, we examined how eye movement density (EMD) measured at 34 to 36 weeks’ gestation related to child development at age 3 years, using two developmental assessment tools. Fetal eye movements were recorded for 60 min. Data from 41 children with complete follow-up at age 3 years were analyzed. EMD was calculated as the number of eye movements per minute during periods with eye movement activity, which reflects the active behavioral state considered a precursor to rapid eye movement (REM) sleep. At 3 years, development was assessed using the Kinder Infant Development Scale and autism-related traits using the Social Responsiveness Scale-2. Sleep was evaluated with caregiver-completed questionnaires and sleep logs at 6 months, 1 year, and 3 years. Higher fetal EMD was associated with greater receptive and expressive language development, whereas lower EMD was linked to higher restricted and repetitive behavior (RRB) scores and an increased likelihood of clinically significant RRB. Moreover, lower EMD predicted later bedtimes at age 1 year. These findings suggest that fetal EMD reflects early maturation of neural circuits and may serve as a noninvasive early biomarker for identifying children at risk of developmental and behavioral difficulties.

The online version contains supplementary material available at 10.1038/s41598-026-35780-3.