Shift work and pregnancy outcomes: a systematic review with meta-analysis of currently available epidemiological studies

Authors

  • M Bonzini,

    1.  Epidemiology and Preventive Medicine Research Centre, Department of Experimental Medicine, University of Insubria, Varese
    2.  Occupational Medicine Unit, Ospedale di Circolo-Macchi Foundation, Varese, Italy
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  • KT Palmer,

    1.  MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK
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  • D Coggon,

    1.  MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK
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  • M Carugno,

    1.  Department of Occupational and Environmental Health, Ca’ Granda Ospedale Maggiore Policlinico IRCCS Foundation, University of Milan, Milan
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  • A Cromi,

    1.  Epidemiology and Preventive Medicine Research Centre, Department of Experimental Medicine, University of Insubria, Varese
    2.  Obstetrics and Gynecology Departement, Ospedale di Circolo-Macchi Foundation, Varese, Italy
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  • MM Ferrario

    1.  Epidemiology and Preventive Medicine Research Centre, Department of Experimental Medicine, University of Insubria, Varese
    2.  Occupational Medicine Unit, Ospedale di Circolo-Macchi Foundation, Varese, Italy
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M Bonzini, Epidemiology and Preventive Medicine Research Centre, University of Insubria, Viale Borri 57, 21100 Varese, Italy. Email matteo.bonzini@uninsubria.it

Abstract

Please cite this paper as: Bonzini M, Palmer K, Coggon D, Carugno M, Cromi A, Ferrario M. Shift work and pregnancy outcomes: a systematic review with meta-analysis of currently available epidemiological studies. BJOG 2011;118:1429–1437.

Background  Varying work schedules are suspected of increasing risks to pregnant women and to fetal wellbeing. In particular, maternal hormonal disturbance arising from sleep deprivation or circadian rhythm disruption might impair fetal growth or lead to complications of pregnancy. Two independent meta-analyses (from 2000 to 2007) reported a small adverse effect of shift work on the risk of preterm delivery (PTD). However, these reviews were based on few high-quality studies.

Objectives  To provide an updated review of the associations of shift work with PTD, low birthweight (LBW), small-for-gestational-age (SGA) infants and pre-eclampsia.

Search strategy and selection criteria  We conducted a systematic search of MEDLINE using combinations of keywords and MeSH terms.

Data collection and analysis  For each relevant paper we abstracted standard details, used to summarise design features and rate methodological quality. We calculated pooled estimates of relative risk (RR) in random-effect meta-analyses.

Main results  We retrieved 23 relevant studies. The pooled estimate of RR for PTD was 1.16 (95% CI 1.00–1.33, 16 studies), but when five reports of poorer methodological quality were excluded, the estimated RR decreased to 1.03 (95% CI 0.93–1.14). We also observed increased RRs for LBW (RR 1.27, 95% CI 0.93–1.74) and for SGA (RR 1.12, 95% CI 1.03–1.22), which varied little by study quality. Little evidence was found on pre-eclampsia.

Conclusions  These findings suggest that overall, any risk of PTD, LBW, or SGA arising from shift work in pregnancy is small.

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