# Development of a quantitative job exposure matrix for standing, walking, and forward bending among pregnant workers – The PRECISE JEM

## TL;DR

This paper creates a detailed job exposure matrix to assess physical activity levels in pregnant workers, aiming to improve understanding of how occupational activities affect pregnancy outcomes.

## Contribution

The study introduces a trimester-specific job exposure matrix for standing, walking, and forward bending among pregnant workers using objective measurements.

## Key findings

- The JEM estimates exposure levels for 1171 job codes using accelerometer data and mixed-effects models.
- Bakers had the highest standing exposure, while waiters and livestock producers had the highest walking and forward bending exposure, respectively.
- Trimester-specific adjustments showed reduced standing time in the third trimester compared to non-pregnant workers.

## Abstract

Occupational physical activity (OPA) during pregnancy has been linked to adverse pregnancy outcomes, but crude exposure assessment remains an issue in causal inference. We aimed to develop a quantitative trimester-specific job exposure matrix (JEM) for standing, walking, and forward bending among pregnant workers.

Accelerometer measurements from 403 female workers across 109 DISCO-08 job codes were obtained in Denmark between January 2023 and June 2024. Full workdays were measured during two weeks among pregnant workers and one week among non-pregnant workers. We used linear mixed-effects models to estimate exposure levels of occupational standing, walking, and forward bending for all 1171 DISCO-08 codes, including age, trimester, and expert ratings as fixed effects, and job codes and workers as random effects.

The between-job variances relative to total variances were 56% for standing, 51% for walking, and 45% for forward bending. The fixed effect trimester reduced standing time by 0.38 hours during the 3rd trimester compared to non-pregnant participants, whereas no differences were observed for walking or forward bending. Based on the trimester-specific JEM for occupational standing time, bakers had the highest exposure (range from non-pregnant to 3rd trimester, 5.41–5.03 hours/workday). For walking and forward bending, the highest exposed jobs from the pregnancy-specific JEM were waiters (1.76 hours/workday) and livestock/dairy producers (1.24 hours/workday), respectively.

The JEM enhances independent objective exposure assessment in epidemiological studies of OPA and pregnancy outcomes and may advance guidelines and potentially prevent adverse pregnancy outcomes.