BJOG release: Swine flu in pregnancy – what to look out for

A new study published in BJOG: An International Journal of Obstetrics and Gynaecology examines how the swine flu virus, Influenza A H1N1 (2009), affects pregnant women.


Clinicians at the KK Women’s and Children’s Hospital in Singapore treated 211 confirmed cases of pregnant women with swine flu between 26 May 2009 and 14 September 2009.  These were women who had fever and/or acute respiratory illness at presentation and a positive diagnosis of having swine flu through a throat swab.       


Most of these patients reported having fever at home but only 62.2% had a fever when they arrived at hospital.  Cough was the most prevalent symptom, occurring in 90.5%.  Other recorded symptoms were: runny nose (62.1%), sore throat (58.8%), muscle ache (32.2%), headache (18%), and breathlessness (13.3%).  Co-morbidities included: asthma (12.8%), hypertension (0.5%) and gestational diabetes (1.9%).  There were two cases of pneumonia, one requiring admission to intensive care. Both recovered.  


The average time between the onset of acute respiratory illness and presentation at hospital was two days and the average time between onset and commencement of treatment was also two days.  The average length of stay in hospital was four days (range: 1 to 6 days) during the containment phase and two (range: 1 to 13 days) in the mitigation phase. 


Antiviral treatment was given to 208 women (three declined treatment as there was a perceived improvement in their health).  They were all treated with Tamiflu except one who requested Relenza.

29.4% were admitted to hospital, mostly because of  breathlessness, sore throat and high temperature. Women admitted were four times more likely to be breathless (a symptom of pulmonary complications) and three times more likely to have co-morbidities, after allowing for all other symptoms.


There were relatively few pregnancy complications; severe morning sickness (2 cases), first trimester miscarriage (3 cases), preterm labour (2 cases), hypertension (1 case) and a suspicious recording of fetal heart rate (1 case).  All patients had a complete recovery from their infection.


The authors commented that the effects of the swine flu infection were relatively mild.  Moreover, Singapore’s previous experience of severe acute respiratory syndrome (SARS) in 2003 meant that it had the infrastructure and systems in place to respond to the outbreak of flu quickly and effectively. Surveillance, isolation and quarantine of suspected cases assisted in early diagnosis and treatment; supported by nationwide public awareness campaigns.  These measures led to early presentation and the subsequent treatment of H1N1-positive pregnant women which may have contributed to the prevention of disease progression.         


Author Dr May Li Lim, from the Department of Maternal-Fetal Medicine at KK Women’s and Children’s Hospital said “This is a largest observational study of pregnant women with A H1N1 (2009) infection published so far. Although we had two cases of respiratory complication (both of whom made a full recovery), the majority of the 211 women recovered without any adverse events from the infection.


“Admission to hospital for monitoring and treatment was more likely to be needed if the women presented with breathlessness and/or concurrent medical illnesses such as asthma and diabetes. Notable features in our cohort included early presentation, early diagnosis and early treatment which could account for the relatively mild disease observed. 


“Our observations suggest that H1N1 (2009) infection in pregnancy may be a relatively benign disease, particularly if diagnosed and treated early. However, our knowledge of the infection is rather limited currently. It is thus prudent to have a cautious approach when managing an obstetric patient with the infection.”


Professor Philip Steer, BJOG editor-in-chief said “This is the largest study on swine flu in pregnancy to date and shows there are benefits to prompt and decisive action in the treatment of confirmed cases.  The case of Singapore is interesting as it demonstrates how the health services in another country coped with the disease and there may be lessons to learn from this example. We will have a better understanding of the H1N1 flu disease as more such studies are published.”   



BJOG: An International Journal of Obstetrics and Gynaecology is owned by the Royal College of Obstetricians and Gynaecologists (RCOG) but is editorially independent and published monthly by Wiley-Blackwell. The journal features original, peer-reviewed, high-quality medical research in all areas of obstetrics and gynaecology worldwide. Please quote ‘BJOG' or ‘BJOG: An International Journal of Obstetrics and Gynaecology' when referring to the journal and include the website: as a hidden link online.


For more information, please contact the RCOG press office on 020 7772 6446 or 020 7772 6357.



Lim M, Chong C, Tee W, Lim W, Chee J. Influenza A/H1N1 (2009) infection in pregnancy—an Asian perspective. BJOG 2010; DOI: 10.1111/j.1471-0528.2010.02522.x.


To view an abstract of the paper, click here.





Date published: 10/02/2010
Published by: Anonymous
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