Pregnant women up to four times more likely to become seriously ill with swine flu

Pregnant women are up to four times more likely to be seriously ill and require hospitalisation when they have swine flu than the general population, new research from the United States suggests.

They are also more likely to die of swine flu or even seasonal flu, meaning they should be prioritised for the flu vaccine as soon as it is available, a study by the US Centers for Disease Control and Prevention (CDC) concluded.

So far, at least two pregnant women are known to have died in Britain after contracting the H1N1 flu strain, while a third had to be flown to Sweden for emergency treatment.

The researchers said that pregnant women with flu symptoms should start taking antiviral treatment as soon as possible, while all expectant mothers should receive a vaccine once one becomes available in coming months.

Little is known about the possible ill-effects of the drugs on the foetus but scientists say their benefits are likely to be greater than the risks.

Data collected by the CDC showed there were 34 confirmed cases of swine flu among pregnant women in the United States between mid-April and mid-May, the first month of the outbreak that has since been declared a global pandemic by the World Health Organisation.

Eleven of the pregnant women, or about a third, were admitted to hospital. The hospitalisation rate for members of the general public infected with swine flu was around eight per cent, or a quarter of the rate among pregnant women, the study showed.

One of the women who became ill in that first month died, but five more pregnant women died of swine flu in the United States during the following month of the outbreak, the report said.

None of the women who died had been given antiviral drugs promptly, within the first 48 hours of symptoms occurring. All of them had developed pneumonia and “acute respiratory distress syndrome” which required them to go on a ventilator, it said.

Denise Jamieson, the CDC’s lead author of the study, which is to be published next month in the Lancet medical journal, said: “We know that in seasonal influenza as well as in pandemic influenza, situations that pregnant women have an increased risk of severe disease and of dying.”

The increased risk is likely to be due to the changes that take place in a woman’s body during pregnancy, she said.

“There are mechanical and hormonal changes in pregnancy, there are changes in the cardiovascular and respiratory systems, there are immunologic changes.

“Lung capacity decreases because as the uterus grows it moves the diaphragm up and there’s basically less room for the lungs. All these changes make pregnant women more susceptible to and more severely affected by certain viruses, including influenza.”

Once a vaccine is available, pregnant women will be a high priority, Dr Jamieson suggests. However, she said she was concerned that women may not come forward to be vaccinated because of fear of any effect on their baby.

The babies of five of the six pregnant women who died during the study period were delivered by Caesarean section.

None had any evidence of influenza infection and all but one, who was born 13 weeks before term, have been discharged in good health, the study said.

Boon Lim, Pandemic Flu Planning spokesman for the Royal College of Obstetricians and Gynaecologists (RCOG) said today: “The World Health Organization (WHO) have stated that pregnant women should be prioritised to receive the swine flu vaccines when these are available. Currently, in the UK, pregnant women are advised to be immunised against the seasonal flu. The recommendation by the CDC to immunise pregnant women from swine flu is an extension of this principle and one which we support.

“The RCOG is working closely with the Department of Health to examine the evidence around safety of vaccination against the swine flu virus. Further guidance on vaccination will be issued in the near future.”

Sir Liam Donaldson, the Chief Medical Officer for England, said that most pregnant women with swine flu would only get mild symptoms but pregnancy brought a higher risk of complications.

Mothers to be were currently advised to continue “normal activities” such as going to work, travelling on public transport and attending events and family gatherings.

“We are not advising pregnant women to cut down on their normal daily activity – some might choose to be very precautionary and not want to go into crowded places, but that is not the advice,” Sir Liam said.


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