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Date of issue: September 2023, Version: 2.3

Sulphur mustard (mustard gas) and nitrogen mustards are alkylating agents with mutagenic and carcinogenic properties. Sulphur mustard is a powerful irritant and vesicant used as a chemical warfare agent. It is absorbed via inhalation, ingestion or through skin contact. Exposure may be associated with severe localised corrosive damage to the skin, eyes, lungs, and in some cases may result in immune system failure and delayed pulmonary damage.

Reports of sulphur mustard exposure in pregnancy are limited. Most animal studies have not demonstrated teratogenicity in the absence of maternal toxicity, although one study in mice suggested a dose-related increase in the risk of cleft palate. Data relating to human parental exposure (mainly paternal) to sulphur mustard during the Iran-Iraq War showed an increased incidence of congenital malformations, including cleft lip and palate. These data are heavily confounded; therefore, it is not currently possible to offer an evidence-based insight into the risk maternal or paternal sulphur mustard exposure poses to a developing fetus.

Sulphur mustard causes similar damage to biological tissues as X-rays and is a DNA alkylating agent that causes chromosome breakage. Exposure to sulphur mustard can result in mutagenicity and carcinogenicity; therefore, adverse pregnancy outcomes may arise due to genetic alterations in gametes/germ cells rather than a direct effect of the chemical on fetal development.

Nitrogen mustards have similar properties to sulphur mustard. No human pregnancy outcome data are available for nitrogen mustard used as a chemical warfare agent. Some nitrogen mustard compounds (such as cyclophosphamide) have been used therapeutically as cytotoxic chemotherapeutic agents and a number of cases of congenital malformations have been reported following human therapeutic exposure.

There are no published guidelines for the treatment of sulphur mustard exposure or inadvertent exposure to nitrogen mustards during pregnancy. Due to the extreme toxicity of these compounds, treatment should be the same as for a non-pregnant patient, with maternal toxicity expected to be a major determinant of fetal risk. For current guidelines on the management of poisoning with sulphur mustard or nitrogen mustards readers are advised to consult TOXBASE or contact UKTIS.

Due to limitations of the available data, it is not currently possible to state that an absence of maternal toxicity excludes the possibility of adverse pregnancy outcomes. The need for enhanced fetal monitoring should be considered on a case-by-case basis where exposures to these compounds have occurred, even in cases which did not result in maternal toxicity. 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.

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 to ensure you are using the most up-to-date version.