Exposure to pesticides during pregnancy may lead to adverse birth outcomes, but only at very high levels of exposure, according to a study published in Nature Communications. The findings, made by evaluating a large dataset from the San Joaquin Valley in California, identify a small target population that could benefit from efforts to reduce pesticide-related birth abnormalities.

Previous studies show that agricultural workers suffer negative health effects from pesticides, but it has been unclear how individuals living near agricultural areas may be affected. Ashley Larsen and colleagues investigate the relationship between pesticide exposure and birth outcomes by analysing 500,000 birth records between 1997-2011 and levels of local pesticide use in the San Joaquin Valley, an area dominated by agriculture. For outcomes, the authors focus on birth weight, gestational age, and birth abnormalities.

Their findings indicate that exposure to very high levels of pesticide use, the top 5% of the sample or at least 4,200 kg of pesticides, during pregnancy increases the probability of adverse birth outcomes (related to birth weight, gestational age, and birth abnormalities) by between 5-9%. Policy interventions targeting those most at risk could reduce pesticide-related birth abnormalities, the authors suggest.