EXPOSURE TO DICHLORVOS IN PREGNANCY

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(Date of issue: November 2018, Version: 1.2)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.

Summary

Dichlorvos is an organophosphate (OP) used as a non-agricultural insecticide and an anthelmintic (worming agent) in animals.

A large number of studies have raised concerns regarding the possible adverse reproductive effects of maternal pesticide exposure as a consequence of residential or occupational proximity to agricultural areas. Adverse pregnancy outcomes reported after such exposures include spontaneous abortion, congenital malformations, stillbirth, intrauterine growth retardation (IUGR), low birth weight and preterm birth. However, such residential and/or occupational proximity may result in concurrent exposure to a number of agricultural chemicals, meaning that measures of exposure are often limited, and furthermore, such proximity may also be associated with other concomitant risk factors for adverse pregnancy outcomes. As such, it is difficult to investigate and draw conclusions regarding the safety of gestational exposure to any one specific pesticide or group of pesticides.

The available data concerning maternal dichlorvos exposure in pregnancy are highly limited. No studies have investigated the risk of congenital malformation following either acute or chronic exposure. A single small retrospective study has suggested a possible association between chronic low dose occupational pesticide exposure, where the list of pesticides used by the exposed study participants included dichlorvos, and an increased risk of spontaneous abortion. The same study did not identify an increased risk of stillbirth, and a second study found no association between dichlorvos exposure specifically and impacts on infant birth weight or preterm delivery risks.

Two case reports of intentional maternal dichlorvos self-poisoning in pregnancy have described fetal and neonatal death (due to extreme prematurity). There are no further data regarding acute dichlorvos poisoning in pregnancy, and as such it is not possible to draw conclusions regarding the maternal or fetal risks. Given the lack of data and the possible adverse effects reported with chronic low dose exposure to pesticides in general, where a pregnancy is ongoing following acute maternal exposure, an increase in risk of adverse fetal effects cannot be ruled out.

There are no guidelines regarding the treatment of dichlorvos poisoning during pregnancy. Maternal toxicity following dichlorvos exposure is likely to be a major determinant of risk to the fetus. Management of the pregnant patient should be the same as for the non-pregnant patient. Where a specific antidote is clinically indicated this should not be withheld on account of pregnancy.

As with all chemicals, unnecessary exposure to dichlorvos should be avoided during pregnancy. However, where occupational exposure is unavoidable, adequate health and safety precautions should be taken to ensure that exposure is well within the recommended exposure limits to minimise the risk of maternal toxicity.

Where exposure to dichlorvos has occurred in pregnancy, enhanced maternal and fetal monitoring may be warranted. Discussion with UKTIS is recommended.

This document is regularly reviewed and updated. Only use full UKTIS monographs downloaded directly from TOXBASE.org to be sure you are using the most up-to-date version. The summaries of these monographs are openly available on UKTIS.org.

This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to health care professionals at www.toxbase.org.

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from TOXBASE.org or UKTIS.org to ensure you are using the most up-to-date version.