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Date of issue: September 2017, Version: 2

Oseltamivir is an oral neuraminidase inhibitor (NI) used in the treatment of influenza infection (licensed for use within 48 hours of the first symptoms), for post-exposure prophylaxis in at-risk groups when influenza is circulating in the community, and to prevent influenza in exceptional circumstances, such as during a pandemic. Oseltamivir is not currently recommended for seasonal prophylaxis against influenza.

Oseltamivir was the NI of choice for use in pregnancy in most countries other than the UK during the 2009 H1N1 pandemic, and as a result is the NI for which there is the most experience of use in pregnancy. In the UK, oseltamivir is therefore currently recommended over zanamivir for the treatment/prophylaxis in pregnant women, except in cases of known or suspected oseltamivir resistance. UK guidelines may, however, change and readers are advised to consult Public Health England guidance directly or to contact UKTIS for current recommendations.

Human data relating to oseltamivir use in pregnancy are, however, still limited. There is currently no signal of a teratogenic effect, or increased risk of other adverse fetal effects, but data for some outcomes are too limited to exclude an increased risk to the fetus. Evidence from the H1N1 pandemic demonstrated that prompt treatment of influenza in pregnancy with neuraminidase inhibitors improves maternal outcomes. The maternal and fetal risks of untreated influenza infection in pregnancy may be significant and the benefits of treatment with oseltamivir are therefore likely to outweigh any theoretical risks to the fetus.

Exposure to oseltamivir at any stage in 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 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.