Scientists believe they are closer to understanding why a condition that can threaten pregnancy occurs.
Pre-eclampsia may have a genetic cause
Pre-eclampsia causes a woman's blood pressure to rise sharply, putting both mother and baby at risk.
Inherited chemical signals between the cells of mother and baby might be to blame, the UK scientists told the Journal of Experimental Medicine.
This might help doctors screen for pre-eclampsia, the Cambridge University team hopes.
Although this common condition has been known about for more than 150 years, doctors still do not understand exactly what causes it.
This makes it hard to predict who will get it or to do much to prevent it, apart from delivering the baby.
Women whose mother or sisters have had it are also more likely to get it, suggesting there might be some inherited factor.
Dr Ashley Moffett and colleagues looked at what was happening in 200 mothers-to-be with pre-eclampsia compared to 201 women with normal pregnancies.
In normal pregnancy, cells in the placenta make sure enough nutrients pass from the mother to the unborn baby by setting up a good blood supply.
To do this, cells from the baby, called trophoblasts, communicate with cells from the mother, called natural killer cells, using chemical signals.
These chemical signals are controlled by genes.
The natural killer cells, which are part of the mother's immune defence system that fights infection and foreign invaders, help to set up the blood vessels in the placenta needed to feed the baby.
In pre-eclampsia, the blood supply is compromised for some reason.
The scientists found the women with pre-eclampsia had different genes controlling the chemical signals than the healthy women.
The researchers believe that certain gene combinations between the baby and the mother could change the way the natural killer cells and the trophoblasts communicate.
Dr Moffett said: "We are only speculating what might happen. Miles more research is needed.
"But this is the first hint that certain gene combinations between the mother and the baby will make some women at risk."
Mike Rich, chief executive of Action on Pre-Eclampsia said: "If it becomes possible to 'read' a genetic code that could identify a woman at greater risk of pre-eclampsia then it would be possible to provide that woman with the extra care and monitoring that is more likely to lead to a positive pregnancy outcome.
"As there is no known cure for pre-eclampsia apart from the delivery of the baby, the development of a test which could identify those women more at risk would have a significant effect on the management of pre-eclampsia," he said.