ABSTRACT Aim This study investigated associations between late‐night shift work and perinatal outcomes. Methods 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. Results 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. Conclusions 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.
Tanaka et al. (Sun,) studied this question.