title: Environmental risk factors of pregnancy outcomes: a summary of recent meta-analyses of epidemiological studies.
abstract: BACKGROUND
  Various epidemiological studies have suggested associations between environmental exposures and pregnancy outcomes. Some studies have tempted to combine information from various epidemiological studies using meta-analysis. We aimed to describe the methodologies used in these recent meta-analyses of environmental exposures and pregnancy outcomes. Furthermore, we aimed to report their main findings.
  
  
  METHODS
  We conducted a bibliographic search with relevant search terms. We obtained and evaluated 16 recent meta-analyses.
  
  
  RESULTS
  The number of studies included in each reported meta-analysis varied greatly, with the largest number of studies available for environmental tobacco smoke. Only a small number of the studies reported having followed meta-analysis guidelines or having used a quality rating system. Generally they tested for heterogeneity and publication bias. Publication bias did not occur frequently.The meta-analyses found statistically significant negative associations between environmental tobacco smoke and stillbirth, birth weight and any congenital anomalies; PM2.5 and preterm birth; outdoor air pollution and some congenital anomalies; indoor air pollution from solid fuel use and stillbirth and birth weight; polychlorinated biphenyls (PCB) exposure and birth weight; disinfection by-products in water and stillbirth, small for gestational age and some congenital anomalies; occupational exposure to pesticides and solvents and some congenital anomalies; and agent orange and some congenital anomalies.
  
  
  CONCLUSIONS
  The number of meta-analyses of environmental exposures and pregnancy outcomes is small and they vary in methodology. They reported statistically significant associations between environmental exposures such as environmental tobacco smoke, air pollution and chemicals and pregnancy outcomes.
authors: Centre for Research in Environmental Epidemiology (CREAL), Barcelona Biomedical Research Park, Dr, Aiguader 88, Barcelona, 08003, Spain. mnieuwenhuijsen@creal.cat
authors: Mark J
authors: MJ
authors: Nieuwenhuijsen
authors: Payam
authors: P
authors: Dadvand
authors: James
authors: J
authors: Grellier
authors: David
authors: D
authors: Martinez
authors: Martine
authors: M
authors: Vrijheid
mesh_terms: D000013:Congenital Abnormalities / Q000453:epidemiology / Q000209:etiology; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D047928:Premature Birth / Q000139:chemically induced / Q000453:epidemiology; D012307:Risk Factors
chemical_list: D004785:Environmental Pollutants