# Associations Between Late‐Night Shift Work and Perinatal Outcomes: A Nationwide Cross‐Sectional Study Using JACSIS and JASTIS Data

## TL;DR

Late-night shift work during pregnancy is linked to higher risks of certain perinatal complications, according to a study using Japanese survey data.

## Contribution

The study is the first nationwide cross-sectional analysis linking late-night shift work to specific perinatal outcomes using JACSIS and JASTIS data.

## Key findings

- Late-night shift work was associated with higher rates of threatened miscarriage, PROM, and hospitalization for health problems.
- Use of the Maternal Health Management and Guidance Card was linked to increased risks of hyperemesis gravidarum and preterm labor among late-night shift workers.
- No significant differences were found in preterm birth, gestational age, mode of delivery, or birth weight between groups.

## Abstract

This study investigated associations between late‐night shift work and perinatal outcomes.

Participants were pregnant women with recorded perinatal outcomes (late‐night shift group, 626 cases; non‐late‐night shift group, 6633 cases) identified from two Japanese Internet surveys. We analyzed the association between late‐night shift work and adverse perinatal outcomes. Furthermore, we examined factors associated with the use of Maternal Health Management and Guidance Cards.

The late‐night shift group had significantly higher rates of threatened miscarriage, premature rupture of membranes (PROM), use of the Maternal Health Management and Guidance Card, health problems requiring hospitalization, fetal health problems, and infectious diseases compared with the non‐late‐night shift group. However, other perinatal outcomes, including preterm birth, gestational age at delivery, mode of delivery, and birth weight, did not differ significantly between groups. Among late‐night shift‐working mothers, those who used the Maternal Health Management and Guidance Card had a higher incidence of hyperemesis gravidarum, threatened miscarriage, and preterm labor than those who did not.

Late‐night shift work during pregnancy may be associated with an increased risk of perinatal complications. The Maternal Health Management and Guidance Card may provide support for pregnant women engaged in late‐night shift work.