title: Swimming and birth weight.
abstract: BACKGROUND
  Swimmers can be exposed to high levels of trihalomethanes, byproducts of chlorination disinfection. There are no published studies on the relation between swimming and birth weight. We explored this relation in a large birth cohort, the Avon (England) Longitudinal Study of Parents and Children (ALSPAC), in 1991-1992.
  
  
  METHODS
  Information on the amount of swimming per week during the first 18-20 weeks of pregnancy was available for 11,462 pregnant women. Fifty-nine percent never swam, 31% swam up to 1 hour per week, and 10% swam for longer. We used linear regression to explore the relation between birth weight and the amount of swimming, with adjustment for gestational age, maternal age, parity, maternal education level, ethnicity, housing tenure, drug use, smoking and alcohol consumption.
  
  
  RESULTS
  We found little effect of the amount of swimming on birth weight. More highly educated women were more likely to swim compared with less educated women, whereas smokers were less likely to swim compared with nonsmokers.
  
  
  CONCLUSIONS
  There appears to be no relation between the duration of swimming and birth weight.
authors.affiliation: Department of Environmental Sciences and Technology, Imperial College of Science, Technology and Medicine, Royal School of Mines, London, UK. m.nieuwenhuijsen@ic.ac.uk
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nieuwenhuijsen
authors.forename: Kate
authors.initials: K
authors.lastname: Northstone
authors.forename: Jean
authors.initials: J
authors.lastname: Golding
mesh_terms: D000328:Adult; D001724:Birth Weight / Q000187:drug effects*; D002713:Chlorine / Q000009:adverse effects; D015331:Cohort Studies; D004739:England; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D013550:Swimming; D013551:Swimming Pools
chemical_list: D002713:Chlorine