Association between Environmental Dioxin-Related Toxicants Exposure and Adverse Pregnancy Outcome: Systematic Review and Meta-Analysis.

Dioxin-related compounds are associated with teratogenic and mutagenic risks in laboratory animals, and result in adverse pregnancy outcomes. However, there were inconsistent results in epidemiology studies. In view of this difference, we conducted a systematic review and meta-analysis to examine this association and to assess the heterogeneity among studies. Comprehensive literature searches were performed to search for relevant articles published in English up to 15 May 2012. In total, we identified 15 studies which included 9 cohort and 6 case control studies. The Cochrane Q test and index of heterogeneity (I(2)) were used to evaluate heterogeneity. In either cohort studies (I(2)=0.89, p<0.0001) or case control studies (I(2)=0.69, p=0.02), significant heterogeneity of risk estimates were observed. Subgroup analyses found no significant increased risk of adverse pregnancy outcome with air dioxin-related compounds exposure (RR=0.99, 95% CI:0.85-1.16), no significant increased risk of spontaneous abortion (SAB) with exposure to food dioxin-related compounds (RR=1.05, 95% CI:0.80-1.37), higher significant risks of low birth weight (LBW) with exposure to food dioxin-related compounds (RR=1.55, 95% CI:1.24-1.94), and higher significant risks of birth defects with maternal solid contaminants dioxin exposure (OR=1.24, 95% CI:1.19-1.29). In conclusion, more evidences are needed to confirm the association between environmental dioxin-related compounds exposure and pregnancy outcome.