Working Conditions In Women With Multiple Pregnancy, The Impact On Preterm Birth And Adherence To Guidelines - A Prospective Cohort Study

BACKGROUND: Women with multiple pregnancies are at risk for maternal complications, such as preterm birth. Hazardous working conditions, e.g. physically demanding work and long and irregular working hours, might increase the risk of preterm birth.

OBJECTIVE: The primary objective of this study is to determine whether certain working conditions up to 20 weeks of pregnancy increase the risk of preterm birth in multiple pregnancies. The secondary objective is to evaluate whether the working conditions of Dutch women with multiple pregnancy have been adjusted to the guidelines of the Netherlands Society of Occupational Medicine (NVAB).

STUDY DESIGN: We performed a prospective cohort study alongside the ProTWIN trial, a multicentre randomised controlled trial that assessed whether a cervical pessary could effectively prevent preterm birth. Women, with paid work > 8 hours a week, completed questionnaires concerning general health and working conditions between 16-20 weeks of pregnancy. Univariable and multivariable logistic regression analyses were performed to identify work-related factors associated with preterm birth (32-36 weeks' gestation) and very preterm birth (< 32 weeks' gestation). We analysed a subgroup of participants who worked more than half a week (> 28 hours). We calculated the proportion of women that showed work-related factors not in accordance with guidelines.

RESULTS: We studied 383 women, of whom 168 (44%) had been randomised to pessary, 142 (37%) to care as usual and 73 (19%) did not participate in the randomised part of the study. After adjusting for confounding variables working hours >28 hours was associated with very preterm birth (n=33, 78%) (aOR 3.0, 95%CI 1.1-8.1), irregular working times with PTB (n=26, 17%) (aOR 2.0, 95%CI 1.0-4.1) and very PTB (n=10, 24%) (aOR 2.7, 95%CI 1.0-7.3). Within a subgroup of 213 participants working > 28 hours per week, multivariable analysis showed that irregular working times (n= 16, 20%) (aOR 3.5, 95%CI 1.2-10.1) and no/little freedom in performance tasks (n=23, 28%) (aOR 3.0, 95%CI 1.3-7.3) were associated with preterm birth. Irregular working times (n=9, 27%) (aOR 3.4, 95%CI 1.0-11.1), requiring physical strength (n=9, 27%) (aOR 5.3, 95%CI 1.6-17.8), high physical workload (n=7, 21%) (aOR 3.9, 95%CI 1.1-13.9) and no/little freedom in performing tasks (n=10, 30%) (aOR 3.2, 95%CI 1.1-9.6) were associated with very preterm birth. Before 20 weeks of pregnancy, 224 (58.5%) women with multiple pregnancy continued to work under circumstances that were not in accordance with the guidelines.

CONCLUSION: In our cohort study, nearly 60% of women with multiple pregnancy, continued to work under circumstances not in accordance with the guidelines to avoid physical and job strain, and long and irregular working hours. Irregular hours were associated with (very) preterm birth, long hours with preterm birth.