title: Preterm Delivery Risk in Relation to Maternal Occupational and Leisure Time Physical Activity Among Thai Women.
abstract: BACKGROUND
  Little is known about the relationship between maternal occupational physical exertion and leisure time physical activity (LTPA) with preterm delivery (PTD) among Thai women, a population that differs in many respects from women in Western countries.
  
  
  OBJECTIVE
  To evaluate associations of maternal occupational physical exertion and LTPA with PTD in aggregate and in subgroups (i.e., spontaneous preterm labor, preterm premature rupture of membrane, medically indicated preterm delivery, moderate preterm delivery [gestational age 32-36 weeks], and very preterm delivery [<32 weeks]) among Thai women.
  
  
  METHODS
  This case-control study included 467 PTD cases and 467 term controls. Maternal occupational exertion during pregnancy, as well as habitual engagement in LTPA before and during pregnancy was assessed using a structured questionnaire administered after delivery. Logistic regression procedures were used to examine relationships between both occupational and leisure time physical activity and PTD.
  
  
  RESULTS
  After controlling for potential confounders, women who reported heavy physical occupational exertion during pregnancy, compared with other women, had a 2.42-fold increased risk of PTD overall [OR=2.42, 95% CI: 1.15, 5.09]. Very PTD [OR=4.57, 95% CI: 1.65, 12.64] and medically indicated PTD [OR=3.79, 95% CI: 1.54, 9.32] were particularly strongly associated with heavy occupational exertion. Maternal participation in LTPA before pregnancy was associated with a 24% reduction in PTD risk overall [OR=0.76, 95% CI: 0.57, 1.00], though no similar pattern in risk reduction was observed for LTPA performed during the first 6 months of pregnancy [OR=0.96, 95% CI: 0.68, 1.36].
  
  
  CONCLUSIONS
  Consistent with some previous reports, we noted that heavy occupational physical exertion is associated with at least a doubling in PTD risk. Patterns of associations of PTD risk with LTPA were less well delineated in this Thai population.
authors.affiliation: Multidisciplinary International Research Training Program, Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA.
authors.forename: Kailey
authors.initials: K
authors.lastname: Nelson
authors.forename: Vitool
authors.initials: V
authors.lastname: Lohsoonthorn
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Williams
keywords: Exercise; Occupational Activity; Physical Activity; Pregnancy; Preterm Delivery