Objectives We examined the association of an array of estimated maternal occupational physical activities and psychosocial stressors during pregnancy with odds for preterm birth (PTB) and small-for-gestational age (SGA).
Methods Data for infants born without major birth defects delivered from 1997 to 2009 whose mothers reported working at least 1 month during pregnancy were obtained from the National Birth Defects Prevention Study. We linked occupational codes to the US Department of Labor's Occupational Information Network, which provides estimates of exposure for multiple domains of physical activity and psychosocial stressors by occupational categories. We conducted factor analysis using principal components extraction with 17 occupational activities and calculated factor scores. ORs for PTB and SGA across quartiles of factor scores in each trimester were computed using logistic regression.
Results Factor analysis grouped occupational domains into 4 groups based on factor loadings. These groups were ‘occupational physical activity’, ‘interpersonal stressor’, ‘automated work’ and ‘job responsibility’. High levels of ‘occupational physical activity’ were significantly associated with SGA (adjusted OR (AOR) for highest quartile compared with lowest quartile of factor score: 1.36; 95% CIs 1.02 to 1.82; p for trend=0.001) and were also positively associated with PTB (AOR: 1.24; 95% CI 0.93 to 1.64; p for trend=0.01). No clear results were observed across domains of psychosocial stressors.
Conclusions Our findings expand understanding of associations between occupational physical activity and psychosocial stressors and PTB and SGA and suggest that additional research is needed to further examine these relationships.
- Preterm birth
- Small-for-gestational age
- physical activity
- psychosocial stressors
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Contributors LJL and ES designed and carried out the study with inputs from PJL and SCT. LJL also drafted and revised the paper with inputs from ES and other coauthors. ATH assisted in the analysis (replication).
Funding This work was supported by the Centers for Disease Control and Prevention (CDC) National Institute for Occupational Safety and Health (NIOSH) Education and Research Center (ERC) (grant number 5T42OH008421) through the Southwest Center for Occupational and Environmental Health. This work was also supported by the CDC Centers for Excellence Award No. U01/DD000494. For the use of the general pooled NBDPS data: this work was supported through cooperative agreements under PA 96043, PA 02081 and FOA DD09-001 from the CDC to the Centers for Birth Defects Research and Prevention participating in the National Birth Defects Prevention Study. For the use of the occupational exposure assessment data: this work was supported by contract 200-2000-08018 from the CDC/NIOSH.
Disclaimer The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC.
Competing interests None declared.
Ethics approval Institutional Review Board, The University of Texas Health Science Center at Houston.
Provenance and peer review Not commissioned; externally peer reviewed.
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