In this study, we show that circulating fetal DNA, which is elevated in pregnancies complicated by preterm labor or preeclampsia, triggers an inflammatory reaction that results in spontaneous preterm birth...
So this is an animal study, but we also have toll-like receptors - TLR9 stands for toll-like receptor 9 - so even though preeclampsia is a human disease this could still be a mechanism in play. Two very interesting things here: one, in the "knockout" mice, where they weren't expressing the relevant genes, fetal DNA did not trigger the inflammatory response. And two, chloroquine blocks the toll-like receptors in question.
Chloroquine is a very, very old malaria drug, and I know nothing about its use in pregnant women. IIRC it isn't used so much these days because malaria is now resistant to it...? Any lurking biologists/public health people please correct me!