This confirms our current understanding - which is important, because if it didn't we'd know we were on the wrong track! - that the placenta is producing the signalling that doesn't have that effect in the mother's body.

That could be because the placenta is sending the wrong signals. That could be because the mother's body isn't receiving them properly. That could be a combination of the two. Most genetic analyses that I've seen think it's both, most of the time, because of the way the inheritance patterns are working, with a stronger influence from maternal predisposition but a substantial parental contribution as well.

so no answers about how to make it happen properly?

[i]We have shown that phagocytosis of trophoblast debris from normal placentae alters the phenotype of macrophages such that they are likely to deviate maternal immune responses towards tolerance and away from inflammation. This may be one of the mechanisms that allow the human fetal allograft to survive in direct contact with the maternal immune system...[/i]

http://www.ncbi.nlm.nih.gov/pubmed/22542910

So in normal pregnancies, when your white blood cells sweep up the bits of material that are released into your bloodstream by the placenta, that turns down inflammatory cytokines and turns up anti-inflammatory cytokines. The placenta is signalling the maternal immune system to calm the heck down.

In our pregnancies, this does not happen properly.