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Date of issue: September 2016
Version: 1.1

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.


C1 esterase inhibitors (C1-INH) are endogenous protease inhibitors belonging to the serpin superfamily of proteins. Exogenous C1 esterase inhibitors, derived from plasma, are used to treat hereditary angioedema (HAE), a condition characterised by a deficiency of this protein.

The available published data concerning the safety of C1 esterase inhibitor use in pregnancy are limited to a small number of case series and case reports, many of which focus on the efficacy of treatment rather than pregnancy outcome. Fetal outcomes have been reported after documented first trimester exposure in 18 pregnancies, with no congenital malformations noted. Exposure in pregnancy has not shown any adverse fetal or neonatal effects attributable to C1 esterase inhibitor, but as experience of use is still extremely limited, a risk of adverse fetal effects cannot be excluded.

Although data on C1 esterase inhibitor use during pregnancy are limited, due to the potential severity of HAE, consensus guidelines advise use as the first line treatment for acute attacks during pregnancy. Severe cases may also require regular C1 INH replacement therapy. Pre-delivery prophylaxis with C1 INH and the availability of C1 INH in the delivery suite should be considered where appropriate.

Exposure to C1 esterase inhibitors at any stage of pregnancy would not usually be regarded as medical grounds for termination of pregnancy or any additional fetal monitoring. However, 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.

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

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

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