Clinical Guidance for Pregnant and Breastfeeding Women with Influenza-Like Illness in the context of the Pandemic H1N1 2009 Virus

Revised March 23, 2010

This guidance is based on current, available scientific evidence and expert opinion about this emerging virus and is subject to review and change as new information becomes available. It should be read in conjunction with relevant provincial and territorial guidance documents. The Public Health Agency of Canada will be posting regular updates and related documents at www.phac-aspc.gc.ca.

Introduction

This guidance document has been prepared by the Public Health Agency of Canada (PHAC) to assist clinicians in managing pregnant and breastfeeding patients presenting with clinical influenza-like-illness (ILI) symptoms in the context of the pandemic (H1N1) 2009 virus (pH1N1) infection. These guidelines should be used in conjunction with information contained in H1N1 PHAC Guidelines for health professionals and in Annex E of the Canadian Pandemic Influenza Plan^[1].

Risks for pregnant women and their fetuses

Pregnant woman and those within 6 weeks post-partum have been identified as being at higher risk of complications and death resulting from pH1N1 infection. Current evidence suggests that the risk of influenza-related morbidity and mortality increases in the second half of pregnancy, especially during the 3^rd trimester^[2],^[3],^[4]. Experience with past pandemics also demonstrates that pregnant women can be affected disproportionately compared to non-pregnant women^[3].

Currently, little is known about whether influenza viruses are transmitted to the fetus through the placenta, although they are not considered to be teratogenic in humans.^[2]

Risks for breastfeeding women and their babies

It is unknown if influenza viruses are transmitted to the baby via human milk. However, it has been shown that women who are breastfeeding and on antiviral treatment transfer less antiviral through the breast milk than if the infant was receiving antivirals for treatment. Continuation of breastfeeding while taking antiviral drugs is unlikely to lead to substantial drug exposure to the infant and adjustment of antiviral dose because of breastfeeding is unncecessary^[2]. Due the anti-infective benefits of human milk for infants and the low dosages of antiviral passed to the baby through breast milk, it is recommended that women continue to breastfeed their babies when taking antiviral medications. Both oseltamivir and zanamivir are considered to be compatible with breastfeeding^[1].

Clinical management of pregnant and breastfeeding women

Although data are limited, the high risk of complications from pH1N1 in pregnant women, especially those in the late stages of pregnancy, are important considerations for treatment and prophylaxis during the current pandemic.

pH1N1 is currently susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza), but resistant to amantadine. Although both oseltamivir and zanamivir may be considered for use during pregnancy^[5],^[6], there are more safety data on oseltamivir than zanamivir in pregnant women^[2],^[6]. While oseltamivir is the treatment of choice; zanamivir may be preferred in pregnant women when nausea and vomiting are present and the National Antiviral Stockpile contains both oseltamivir and zanamivir.

Clinicians will want to strongly consider oseltamivir or zanamivir for all pregnant women who develop clinical features of ILI, especially in their second and third trimesters and within 6 weeks post-partum. Clinical ILI symptoms usually include: sudden onset of cough and fever; and commonly: sore throat, coryza, fatigue/malaise/prostration, myalgias/arthralgias, headache, decreased appetite, and gastrointestinal symptoms (one or more of nausea, vomiting and diarrhea). Pregnant women are also more likely to report shortness of breath^[7]. Since there appears to be an increased mortality risk in pregnant women compared to the general population, pregnant women need increased medical attention and antiviral therapy as soon as possible and within 48 hours of symptom onset. However, consideration may be given to starting treatment on pregnant woman hospitalized with confirmed, probable, or suspected pandemic H1N1 even after 48 hours of symptom onset.

It is recommended that all pregnant women be informed of their increased risk of complications if they become ill with influenza, including pH1N1, and the need for a prompt assessment by a health care professional should be stressed. This is especially important information for pregnant mothers of young children with ILI. An information sheet for pregnant women and pandemic H1N1 is available at http://www.phac-aspc.gc.ca/alert-alerte/h1n1/pdf/Factsheet_Pregnant_breastfeeding.pdf

The treatment dosing is the same for pregnant women as other adults: oseltamivir (Tamiflu (External link) ): 75 mg capsule twice/day for 5 days or Zanamivir (Relenza (External link) ): Two 5mg inhalations (10mg total) twice/day for 5 days. More information can be located in the appropriate product monograph.

Adverse reaction reporting

Reports of adverse reactions to antiviral medications are an important source of information that will help guide their safest and most effective use. Please promptly report any suspected serious adverse reactions involving an antiviral medication as per local or provincial/territorial requirements to Health Canada at: Adverse Reaction Reporting, Marketed Health Products (External link) or call: 1-866-234-2345.

References