title: Maternal Leisure-time Physical Activity and Risk of Preterm Birth: A Systematic Review of the Literature.
abstract: Preterm birth is a leading cause of infant death and the role of maternal physical activity on this risk remains unclear. This systematic review examined low, moderate and vigorous leisure-time physical activity (LTPA) during pregnancy and the outcome of preterm birth.
  
  
  
  Key words related to preterm birth and physical activity were used to search relevant databases (Medline, Cochrane, CINAHL, Sports Discuss and Scopus). Studies were excluded if they did not measure physical activity as an exposure in pregnant women, did not provide information on gestational age at delivery, and were not published in English. All study designs and sample sizes were considered.
  
  
  
  The search generated 1472 studies. There were 27 studies included in this review of which 23 received high quality reporting scores. Eleven studies reported a lower risk of preterm birth for women who performed LTPA during pregnancy, while 14 studies reported null findings. Only 2 studies detected a significantly higher risk of preterm birth with LTPA during pregnancy.
  
  
  
  This review of literature up to 2014 provides additional evidence to support the assertion that healthy pregnant women can engage in low, moderate, and even some vigorous levels of LTPA without risk for preterm birth.
authors.affiliation: Dept of Exercise and Nutrition Sciences, Milken Institute School of Public Health, The George Washington University, Washington, DC.
authors.forename: Mira
authors.initials: M
authors.lastname: Kahn
authors.forename: Kim
authors.initials: K
authors.lastname: Robien
authors.forename: Loretta
authors.initials: L
authors.lastname: DiPietro
mesh_terms: D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007899:Leisure Activities; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*; D012306:Risk