Scientists have suggested a lung infection may be linked to a pregnancy complication which can put the lives of mothers and babies at risk.
The cause of pre-eclampsia is unknown
An Imperial College team found women who had pre-eclampsia had higher levels of antibodies to chlamydia pneumoniae.
The British Journal of Obstetrics and Gynaecology study says the infection could play a role in pre-eclampsia.
The condition affects around 3% of all pregnant women, but scientists do not fully understand what causes it.
In a normal pregnancy, the developing foetus signals to the mother's body to widen the blood vessels to the placenta, which supplies oxygen and nutrients.
However, in pre-eclampsia these blood vessels grow narrower.
The condition, which is a major cause of maternal and perinatal mortality worldwide, has been found to be more common in women having their first babies.
Chlamydia pneumoniae is a different type of chlamydia to that which causes the sexually transmitted infection.
It has also been found to infect and multiply in the lining of cell walls in blood vessels, leading researchers to link it to atherosclerosis, the narrowing of blood vessels and other cardiovascular conditions.
The Imperial College team decided to examine whether C. pneumoniae was also linked to pre-eclampsia, another condition in which the lining of the blood vessels is affected.
Ninety-one pregnant women, 32 of whom had a history of pre-eclampsia, were studied.
It was found that those women who had had pre-eclampsia had higher levels of antibodies to the infection.
It is possible that this infection plays a role in the origin of a disease in a small number of women who are predisposed to the condition.
Dr Catherine Williamson, who led the research, said: "These preliminary data support the findings of other studies that suggest that chlamydia pneumoniae infection may be associated with pre-eclampsia.
"If our results are supported by a larger study, these results will have implications for the investigation and treatment of women with this important disease of pregnancy."
She added: "It may be possible to screen women in the early stage of pregnancy, and to possibly look at using drugs."
But she said: "Pre-eclampsia is a multi-factoral condition."
Mr Peter Bowen-Simpkins, Royal College of Obstetricians and Gynaecologists told the BBC News Website: "This is an exciting development and may throw some light on the cause of one of the most important diseases of pregnancy.
"There has been so much research carried out into pre-eclampsia over the last 100 years and no one's come to any conclusions. This research is the beginning, and may lead on to bigger things.
"If it can be shown that, in some cases, it definitely is to do with this bacteria, it may be a indication for screening and treatment.