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.
This sounds like true progress. Over the past 5-10 years we may have begun to disentangle the mechanisms of a terrible disorder. Pre-eclampsia is usually managed successfully, but every so often a healthy woman dies in an particularly terrible manner.
Amazing to think that the cells we named "Natural Killer (NK)" help build the placenta. Maybe they could be renamed? (The consequences of naming in biology are manifold.)
There has been much speculation about the evolutionary basis of pre-eclampsia. Mostly it focuses on the degree to which a mother and a fetus are in a state of low level war, reflecting competition between parternal and maternal genes. The paternal genes want "more" from the mother's body, the maternal genes want "less". This is an ancient war -- and only the dynamic tension between the two permits a healthy baby and mother. If the paternal genes lose the baby dies, if the maternal genes lose the mother and baby die.
That's the theory anyway. Maybe we'll find out more soon. I'm not sure how the "intelligent design" folks explain there kinds of mechanisms.