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Date of issue: April 2020, Version: 3

Ethylenethiourea (ETU) is used in the rubber industry and in the production of some fungicides. 

Data relating to pregnancy outcomes following ETU exposure are scarce. No increased risk of malformation was observed in a retrospective case-series investigating the offspring of women who worked in the rubber industry and a prospective cohort study found no significant differences in neurodevelopmental outcomes between exposed infants and population norms. However, due to the extremely limited data an evidence-based assessment of fetal risk following either acute or chronic exposure to ethylenethiourea during pregnancy is not possible. 

Teratogenicity has been observed in some (but not all) animal species following in utero ethylenethiourea exposure. Various structural malformations, growth restriction, thyrotoxicity, hepatotoxicity and behavioural abnormalities have been reported in rats. Ethylenethiourea consistently induces anorectal malformations in a high percentage of rat embryos and is therefore used as a positive control for teratogenicity in preclinical studies.  It is not known whether there are similar risks to the human fetus.

As with all chemicals, unnecessary exposure to ethylenethiourea should be avoided during pregnancy. Where occupational exposure is unavoidable, precautions should be taken to ensure that exposure is well within the recommended exposure limits and not associated with toxic symptoms.

Following ethylenethiourea exposure in a pregnant woman, maternal toxicity is likely to be a major determinant of risk to the fetus. However, due to a lack of data relating to the human teratogenicity of ethylenethiourea, it is not currently possible to state that an absence of maternal toxicity excludes the possibility of adverse events occurring in the developing fetus.

There are no published guidelines on the management of poisoning with ethylenethiourea compounds during pregnancy and pregnant patients should be managed as for non-pregnant patients. Thiourea compounds can interfere with thyroid function and maternal thyroid status should be checked following any exposure to ethylenethiourea.

Exposure to ethylenethiourea at any stage in pregnancy may also confer a risk to the fetus. The need for additional fetal monitoring following maternal exposure to ethylenethiourea needs to be assessed on a case-by-case basis. A detailed fetal anomaly scan to include assessment of the fetal thyroid should be considered. Thyroid and liver function should be checked in all exposed neonates at birth. Other risk factors may also 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. Discussion with UKTIS is recommended in all cases.

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 NHS health care professionals who are logged in.

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.

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