Non-traditional work schedules are suspected to present risks to pregnant women and to fetal welbeing. Maternal hormonal disturbance arising from sleep deprivation or circadian rhythm disruption, may affect fetal growth and pregnancy complications. Two independent meta-analyses (published in 2000 and 2007) found a small adverse effect of shift work on preterm delivery (PTD) risk. However, these reviews were based on a small number of high quality studies.
In this presentation, we provide an updated systematic review of the association between shift work and PTD or baby growth retardation (SGA). We conducted a systematic search of MEDLINE using combination of keywords and MeSH terms. For each relevant paper we abstracted standard details that were used to summarize design futures and to rate their methodological quality. We calculated pooled estimates of risks for PTD and SGA in a random-effect meta-analysis.
We retrieved 23 studies reporting risk estimates for PTD or SGA among women exposed to shift work. We calculated a pooled estimates for PTD=1.158 (95%CI 1.005-1.335), but the strength of the association was attenuated by some evidence of possible publication bias and when studies with poor methodological quality (incomplete reporting, spurious exposure or potential bias) were excluded, the risk estimate was slightly reduced (1.094, 95%CI 0.948-1.263. We also observed an increased risk for SGA (=1.120, CI95% 1.025-1.224), that was confirmed after excluding poor-quality studies. We also found an increased work-absence rate among exposed women and some evidence of a beneficial effect of preventive measures taken early in pregnancy.
Our data seem to confirm small adverse effects of shift works on pregnancy outcomes, suggesting that working women should receive complete information about this potential reproductive hazard and that a change from shift work should be permitted since early in pregnancy. Evidence about others adverse reproductive outcomes will be critically discussed.
Matteo Bonzini, MD, MPH, is Assistant Professor of Occupational Health in the Faculty of Medicine of the University of Insubria in Varese, Italy. He obtained his MD from the School of Medicine at the University of Milan, and his Masters in Epidemiology from the University of Turin.
Dr. Bonzini’s research interests include: shift work and pregnancy complications, air pollution exposure during pregnancy and neonatal health, occupational physical activity and pregnancy outcomes, musculoskeletal disorders, benzene exposure and cancer risk, and the genetic epidemiology of lung cancer and smoking.