The government is advising expectant mothers to avoid unnecessary travel and crowded places, as the NHS seeks to "clarify" its guidance to people in high-risk groups on how to reduce the chances of contracting swine flu.
The Department of Health said mothers-to-be were more vulnerable to any type of flu and sought to defuse a row over whether delaying pregnancy could cut a woman's risk of catching the virus or reduce its severity.
GPs have accused the National Childbirth Trust (NCT) of scaremongering after it advised women to consider postponing trying to become pregnant until the swine flu pandemic has passed.
The Department of Health insisted couples were not being advised to delay conceiving during outbreak and said there was "no need to panic".
A spokeswoman said swine flu was so far proving to be mild for most people "although for a small number it has been severe".
She added: "We advise everybody to plan their pregnancy carefully; we are not advising women not to conceive.
"Mums-to-be are more vulnerable to any type of flu. It is particularly important that anyone who has existing health problems and is thinking about starting a family should talk to their GP first, as they normally would."
Holidaymakers were also advised to take medication such as paracetamol with them and avoid public places if they fall ill. A party of British schoolchildren were kept in quarantine in Beijing after members of their party were diagnosed with swine flu.
The NCT, Britain's leading parenting charity, said delaying pregnancy could cut a woman's risk of catching the virus or reduce its severity. "Expectant mothers are thought to be at greater risk from the virus because the immune system is naturally suppressed during pregnancy to ensure it does not reject the baby," said Belinda Phipps, the trust's chief executive.
"Early figures also suggest it takes expectant mothers longer to fight off the disease. Most would still only develop a mild case, but in rare cases symptoms could lead to premature labour, a miscarriage or even cause birth defects."
The comments were condemned as "scaremongering" by Professor Steve Field, chairman of the Royal College of General Practitioners.
"This is one of the few times I have disagreed with the NCT," Field said. "Although technically correct, its advice is a completely disproportionate reaction. I don't believe it's appropriate to give out this sort of message, because it adds to the sense of hysteria and panic that seems to be engulfing the nation.
"At its worse, the pandemic will hit 30% of the population, of whom 0.3% might die. The number of pregnant women in this group is tiny," he added. "Anyway, pandemics last for two to three years. It is very difficult for people to plan around that, even if they want to."
It emerged last week that pregnant women and very young children were among key swine flu risk groups, according to hospital figures and the age profiles of those who had already died. Among the victims was Ruptara Miah, 39, who died of swine flu last Monday, shortly after giving birth prematurely.
The Royal College of Midwives gave fresh advice yesterday on giving expectant women antiviral drugs, saying that pregnant women with flu symptoms could be given a course of Relenza, via an inhaler. The Health Protection Agency altered its advice last week after Miah's death, to include children under five in the category of those "predominantly affected".
The health department has also warned that women who are part-way through a fertility programme would "need to balance possible difficulties in deciding to interrupt the programme by choice or because the service becomes unavailable, against the urgency to complete the programme and the safety of the pregnancy and newborn during a pandemic".
Bruce Mann, the director of the Civil Contingencies Secretariat, which co-ordinates the government's response to national emergencies, has written to businesses warning that he expects there will be significant absences from work. In a letter to the Business Advisory Network for Flu, Mann suggests: "Absence rates for illness may reach 12% of the workforce in the peak weeks of the current wave and up to 9% by the end of August."
The letter says: "These figures cover the proportion of the workforce who may be absent from work because they are ill themselves or because they are looking after ill children." While supermarket chains and banks have drawn up contingency plans to ensure that food and cash continue to move around the country, the government has also issued guidance to ensure that a stripped-down version of civic society will function.
The most controversial proposal would allow the Crown Prosecution Service to hand out more cautions or fines, rather than take offenders to court for relatively minor offences such as theft, drugs and some crimes involving violence against the person. However, a CPS spokeswoman said that any decision on issuing new guidelines on conditional cautions would be left to the director of public prosecutions.
A 59-page government document, entitled "planning for possible influenza pandemic: a framework for planners preparing to manage deaths", outlines how "inflatable storage structures", which "come in various designs and can be customised and deployed to a range of terrains", could be used as temporary mortuaries. Shipping containers could also be used, although the document notes: "These are likely to require shrouding, body racking and power generators."
Faith groups may also have to consider their role. Guidance issued by the government suggests: "Those arranging and conducting funerals should prepare for basic and shorter services at the chapel, or for memorial services to be held at other venues (eg the home or place of worship)." It also suggests: "Local planners should also consider with crematorium managers whether it is practical for crematoria to move to 24/7 working."
