A systematic review of benzene exposure during pregnancy and adverse outcomes on intrauterine development and birth: still far from scientific evidence.

The effect of exposure to some air pollutants during pregnancy on embryonic and fetal development has been evaluated by several studies, but it has not been well defined. The main objective of this study was to use a systematic review to evaluate the relationship between air benzene exposure in pregnant women and possible negative effects on intrauterine development and negative outcomes at birth. After a systematic literature search, we identified five peer-reviewed studies with quantitative results regarding the association between benzene exposure during pregnancy and adverse outcomes on intrauterine development and at birth. The characteristics of the study design and population of each selected article were summarised. There was evidence for the association between an increase in preterm birth or a decrease in biparietal diameter growth with maternal exposure to benzene or early exposure to aromatic solvents, while the evaluation of the relationship between benzene exposure during pregnancy and other parameters (i.e., birthweight, fetal weight, birth length, head circumference growth, fetal femur length, and abdominal circumference) returned no clear conclusions. Further studies are required to confirm and clarify the possible adverse outcomes of benzene exposure during pregnancy. Recommendations for future studies are related to the most appropriate strategies for outcomes and exposure assessment and the evaluation of "individual genetic susceptibility", which is a possible confounding factor in this kind of studies.