Will find the link as soon as I can (browser crashed before I could save) but there is some good evidence to suggest that regular sex with the baby's father, particularly oral sex (if you swallow) can help introduce pathogens (I think that's what they are) that prevent the mother's immune system attacking their presence with its auto immune response and that this is connected to pre eclampsia.
I suggest you keep this to yourselves though or you may regret it !