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Date of issue: June 2022, Version: 3

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A corresponding patient information leaflet on USE OF TRASTUZUMAB IN PREGNANCY is available.

Trastuzumab is a recombinant humanised IgG1 monoclonal antibody against the human epidermal growth factor receptor 2 (HER2). Trastuzumab is indicated in the treatment of HER2 positive early breast cancer, metastatic breast cancer, and metastatic gastric cancer, where tumours have either HER2 overexpression or HER2 gene amplification.

There are very limited data on use of trastuzumab in pregnancy, therefore an evidence-based assessment of risk to the fetus is not currently possible. Only one case of congenital malformation (renal agenesis) has been observed following first trimester exposure to trastuzumab; however, data are limited to 25 exposed pregnancies. Oligohydramnios/anhydramnios has been observed in >60% of case reports documenting exposure during pregnancy, and 100% of pregnancies where trastuzumab exposure continued in the second or third trimester. Effects on miscarriage, fetal growth, preterm delivery, stillbirth, neonatal complications, neurodevelopment and carcinogenicity risk in offspring have not been adequately studied. The manufacturer advises that effective contraception should be used during treatment with trastuzumab and for seven months after treatment has concluded.

Trastuzumab has been associated with an increased risk of reversible cardiac dysfunction in the non-pregnant patient, which may be exacerbated during pregnancy by the additional strain placed on maternal cardiac function.

Enhanced monitoring of maternal cardiac function and amniotic fluid volume is recommended if trastuzumab treatment is ongoing during pregnancy. 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.

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.