Summary
Diquat and paraquat are non-selective dipyridyl herbicides. Paraquat is no longer used in the UK. Diquat is available in commercial formulations such as Reglone® and Weedol®.
Numerous studies have raised concerns about the possible reproductive effects of pesticide and herbicide exposure as a consequence of residential proximity to agricultural fields or working in agricultural areas. However, data specifically documenting pregnancy outcome following in utero chronic low level exposure to paraquat are scarce. There are no data on pregnancy outcomes for chronic low level diquat exposure.
Adverse effects including structural malformation, pulmonary fibrosis, premature closure of the ductus arteriosus and increased resorptions have been reported in reproductive toxicity studies in some animal species. Human data are much more limited but suggest a high risk of fetal demise or toxicity following maternal ingestion. The possibility of the adverse fetal effects observed in preclinical studies should therefore be considered in such cases. No published data on the possible adverse effects of acute diquat exposure during human pregnancy have been located, but risk to the fetus is likely to be significant in cases of maternal poisoning.
One study reported a statistically significant increase in risk of childhood leukemia following pre-gestational parental exposure to paraquat.
As with all chemicals, unnecessary exposure to these herbicides should be avoided during pregnancy. However, where occupational exposure is unavoidable then precautions should be taken to ensure that exposure is well within the recommended exposure limits and not associated with symptoms of maternal toxicity.
Management of a pregnant patient exposed to diquat or paraquat should be as for the non-pregnant patient. Maternal toxicity as a result of exposure is likely to be a major determinant of the risk posed to a developing fetus. However, due to limitations in the available data, it is not currently possible to state that an absence of maternal toxicity excludes the possibility of adverse pregnancy outcomes.
Additionally, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments. Enhanced antenatal monitoring may be warranted following maternal exposure to diquat or paraquat. Discussion with UKTIS is recommended in all cases of maternal exposure.
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