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Influence of shift work on early reproductive outcomes: a systematic review and meta-analysis

Influence of shift work on early reproductive outcomes: a systematic review and meta-analysis
Influence of shift work on early reproductive outcomes: a systematic review and meta-analysis
OBJECTIVE:
To determine whether an association exists between shift work and early reproductive outcomes.
DATA SOURCES:
MEDLINE, Embase, and Web of Science were searched. Additional sources included Google Scholar, the Cochrane Library, online publications of national colleges, the ClinicalTrials.gov, and references of retrieved papers.
METHODS OF STUDY SELECTION:
Included studies compared female shift workers (work outside 8:00 AM to 6:00 PM) with nonshift workers with menstrual disruption (cycles less than 25 days or greater than 31 days), infertility (time-to-pregnancy exceeding 12 months), or early spontaneous pregnancy loss (less than 25 weeks).
TABULATION, INTEGRATION, AND RESULTS:
Two reviewers extracted adjusted and raw data. Random effect models were used to pool data weighting for the inverse of variance. Assessments of heterogeneity, bias, and subgroup analyses were performed. Sixteen independent cohorts from 15 studies (123,403 women) were subject to analysis. Shift workers had increased rates of menstrual disruption (16.05% [2,207/13,749] compared with 13.05% [7,561/57,932] [n=71.681, odds ratio {OR} 1.22, 95% confidence interval {CI} 1.15-1.29, I 0%]) and infertility (11.3% [529/4,668] compared with 9.9% [2,354/23,811] [OR 1.80, 95% CI 1.01-3.20, I 94%]) but not early spontaneous pregnancy loss (11.84% [939/7,931] compared with 12.11% [1,898/15,673] [n=23,604, OR 0.96, 95% CI 0.88-1.05, I 0%]). Night shifts were associated with increased early spontaneous pregnancy loss (n=13,018, OR 1.29, 95% CI 1.11-1.50, I 0%). Confounder adjustment led to persistent relationships between shift work and menstrual disruption (adjusted OR 1.15, 95% CI 1.01-1.31, I 70%) but not infertility (adjusted OR 1.11 95% CI 0.86-1.44, I 61%). The association between night shifts and early spontaneous pregnancy loss remained (adjusted OR 1.41 95% CI 1.22-1.63, I 0%).
CONCLUSION:
This review provides evidence for an association between performing shift work and early reproductive outcomes, consistent with later pregnancy findings. However, there is currently insufficient evidence for clinicians to advise restricting shift work in women of reproductive age.
0029-7844
99-110
Stocker, L.J.
a5ff11ab-2eae-44f5-81e0-42cb67343f8e
Macklon, N.S.
7db1f4fc-a9f6-431f-a1f2-297bb8c9fb7e
Bewley, S.J.
f9688cb5-45b4-4134-8679-dfaa69f2ff73
Cheong, Y.
4efbba2a-3036-4dce-82f1-8b4017952c83
Stocker, L.J.
a5ff11ab-2eae-44f5-81e0-42cb67343f8e
Macklon, N.S.
7db1f4fc-a9f6-431f-a1f2-297bb8c9fb7e
Bewley, S.J.
f9688cb5-45b4-4134-8679-dfaa69f2ff73
Cheong, Y.
4efbba2a-3036-4dce-82f1-8b4017952c83

Stocker, L.J., Macklon, N.S., Bewley, S.J. and Cheong, Y. (2014) Influence of shift work on early reproductive outcomes: a systematic review and meta-analysis. Obstetrics and Gynecology, 124 (1), 99-110. (doi:10.1097/AOG.0000000000000321). (PMID:24901274)

Record type: Article

Abstract

OBJECTIVE:
To determine whether an association exists between shift work and early reproductive outcomes.
DATA SOURCES:
MEDLINE, Embase, and Web of Science were searched. Additional sources included Google Scholar, the Cochrane Library, online publications of national colleges, the ClinicalTrials.gov, and references of retrieved papers.
METHODS OF STUDY SELECTION:
Included studies compared female shift workers (work outside 8:00 AM to 6:00 PM) with nonshift workers with menstrual disruption (cycles less than 25 days or greater than 31 days), infertility (time-to-pregnancy exceeding 12 months), or early spontaneous pregnancy loss (less than 25 weeks).
TABULATION, INTEGRATION, AND RESULTS:
Two reviewers extracted adjusted and raw data. Random effect models were used to pool data weighting for the inverse of variance. Assessments of heterogeneity, bias, and subgroup analyses were performed. Sixteen independent cohorts from 15 studies (123,403 women) were subject to analysis. Shift workers had increased rates of menstrual disruption (16.05% [2,207/13,749] compared with 13.05% [7,561/57,932] [n=71.681, odds ratio {OR} 1.22, 95% confidence interval {CI} 1.15-1.29, I 0%]) and infertility (11.3% [529/4,668] compared with 9.9% [2,354/23,811] [OR 1.80, 95% CI 1.01-3.20, I 94%]) but not early spontaneous pregnancy loss (11.84% [939/7,931] compared with 12.11% [1,898/15,673] [n=23,604, OR 0.96, 95% CI 0.88-1.05, I 0%]). Night shifts were associated with increased early spontaneous pregnancy loss (n=13,018, OR 1.29, 95% CI 1.11-1.50, I 0%). Confounder adjustment led to persistent relationships between shift work and menstrual disruption (adjusted OR 1.15, 95% CI 1.01-1.31, I 70%) but not infertility (adjusted OR 1.11 95% CI 0.86-1.44, I 61%). The association between night shifts and early spontaneous pregnancy loss remained (adjusted OR 1.41 95% CI 1.22-1.63, I 0%).
CONCLUSION:
This review provides evidence for an association between performing shift work and early reproductive outcomes, consistent with later pregnancy findings. However, there is currently insufficient evidence for clinicians to advise restricting shift work in women of reproductive age.

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Green J meta analysis - Accepted Manuscript
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Accepted/In Press date: July 2014
e-pub ahead of print date: July 2014
Published date: July 2014
Organisations: Human Development & Health

Identifiers

Local EPrints ID: 367176
URI: https://eprints.soton.ac.uk/id/eprint/367176
ISSN: 0029-7844
PURE UUID: bda86fad-da23-4bda-a355-488aceb7ab36
ORCID for Y. Cheong: ORCID iD orcid.org/0000-0001-7687-4597

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Date deposited: 23 Jul 2014 15:37
Last modified: 07 Aug 2019 00:39

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