My colleague at New Scientist looked into this issue during the swine flu outbreak, and concluded that the risks of getting flu during pregnancy far outweigh any (as yet unproven) dangers that might result from vaccination.
See: www.newscientist.com/article/dn17920-flu-in-pregnancy-leaves-a-mean-legacy.html
Also pasting the text below:
Pregnant women are at the front of the queue for swine flu vaccine as distribution starts this month in the US, UK and elsewhere. It is well known that their suppressed immunity puts them at greater risk; less widely recognised is the evidence that flu can harm their babies.
Caleb Finch of the University of Southern California in Los Angeles and his colleagues report that men who were in their mother's womb during the September peak of the 1918 flu pandemic have been 23 per cent more likely to have had heart attacks since they turned 60 than siblings who were either not yet conceived or already born. The risk has been 17 per cent greater for women.
And when men in this group enlisted in the second world war, they averaged 1.25 millimetres shorter than normal, suggesting the virus affected growth and development generally. With so many people at increased risk of heart disease, Finch calculates that even babies whose mothers had mild symptoms must have been affected.
Flu poses still more risks for the unborn. In April, it was reported that men who were in the womb in early 1970, when a mild flu pandemic hit Norway, had lower scores in army intelligence tests than normal. A 2006 study showed that babies in the womb in September 1918 went on to have lower incomes and education levels, and higher rates of disability. And babies whose mothers have ordinary flu in early pregnancy are 7 times as likely to develop schizophrenia.
Animal experiments, says Finch, suggest the culprit may be signalling chemicals called cytokines that are involved in inflammation.
Balance of risk
The US Centers for Disease Control and Prevention says pregnant women in the US are 6 times as likely to die of the disease as other people. Yet such women and their doctors may avoid the swine flu vaccine out of caution about pharmaceuticals during pregnancy. This seems unjustified: the US has launched a safety trial of the vaccine in pregnant women, but similar flu vaccines have been safe.
"Mothers think they're protecting their baby by not getting the flu vaccine," says bioethicist Margaret Little of Georgetown University in Washington DC, who specialises in women's medicine. "In fact, the flu is a more dangerous risk than the vaccine."
Journal reference: Journal of Developmental Origins of Health and Disease, DOI: 10.1017/S2040174409990031