This study from Alberta, Canada raises some potentially very important concerns about the possible environmental risks for women who live close to fracking sites. The increased risk for babies of major congenital anomalies, and being small-for-gestational age, suggests an effect in pregnancy that is there from the outset and may be mediated through placental function. With larger numbers it is possible that other effects could be seen which are mediated via placental dysfunction such as stillbirth. The fact that the risk is apparently highest for those who were exposed to more than 100 sites suggests a dose-response relationship which adds to the biological plausibility. Given the seriousness of these findings it is important to try and replicate this work in other settings.

This is an interesting study but it is highly likely the observed effect actually relates to diet rather than distance to fracking sites. There is good evidence from a Cochrane Systematic Review and multiple randomised trials that diets low in omega 3 fatty acids independently contribute to risk of preterm birth and thus birthweight, and fracking sites are located near populations with poor omega-3 diets. The authors did not collect dietary information about omega-3 and this was therefore not adjusted for in the study. I suspect most of the effect is dietary rather than related to fracking sites. A prospective study that captures diet and blood omega-3 levels and controls for these would be required before any cause and effect could be drawn from this study.