title: Environmental tobacco smoke and fetal health: systematic review and meta-analysis.
abstract: OBJECTIVE
  To determine the effects of environmental tobacco smoke (ETS) exposure on birth outcomes.
  
  
  METHODS
  A systematic review and meta-analysis was performed in accordance with MOOSE guidelines. MEDLINE, EMBASE, CINAHL and LILACS (up to October 2007), were searched and also reviews and reference lists from publications, with no language restrictions. Pooled mean differences and odds ratios (ORs) with 95% confidence intervals were estimated using data extracted from papers, based on random effect models.
  
  
  METHODS
  Comparative epidemiological studies.
  
  
  METHODS
  Pregnant women or women who have given birth.
  
  
  METHODS
  Maternal exposure to ETS during pregnancy.
  
  
  METHODS
  Mean birth weight and proportion of premature infants.
  
  
  RESULTS
  58 studies were included; 53 used cohort designs, 23 ascertaining ETS exposure prospectively and 30 retrospectively; 5 used case-control designs. In prospective studies, ETS exposure was associated with a 33 g (95% CI 16 to 51) reduction in mean birth weight, and in retrospective studies a 40 g (95% CI 26 to 54) reduction. ETS exposure was also associated with an increased risk of low birth weight (birth weight <2500 g; prospective studies: OR 1.32, 95% CI 1.07 to 1.63; retrospective studies: OR 1.22, 95% CI 1.08 to 1.37). The risk of small for gestational age (<10th centile) birth was significantly associated with ETS exposure only in retrospective studies (OR 1.21, 95% CI 1.06 to 1.37). There was no effect of ETS exposure on gestational age.
  
  
  CONCLUSIONS
  Exposure of non-smoking pregnant women to ETS reduces mean birth weight by 33 g or more, and increases the risk of birth weight below 2500 g by 22%, but has no clear effect on gestation or the risk of being small for gestational age.
authors.affiliation: Dr J Leonardi-Bee, Division of Epidemiology and Public Health, University of Nottingham, Clinical Sciences Building, Nottingham NG5 1PB, UK; jo.leonardi-bee@nottingham.ac.uk.
authors.forename: J
authors.initials: J
authors.lastname: Leonardi-Bee
authors.forename: A
authors.initials: A
authors.lastname: Smyth
authors.forename: J
authors.initials: J
authors.lastname: Britton
authors.forename: T
authors.initials: T
authors.lastname: Coleman
mesh_terms: D005260:Female; D005317:Fetal Growth Retardation / Q000209:etiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development; D007236:Infant, Small for Gestational Age / Q000254:growth & development; D018811:Maternal Exposure / Q000009:adverse effects; D011247:Pregnancy; D011295:Prenatal Care / Q000592:standards; D011297:Prenatal Exposure Delayed Effects / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution