lack of immune tolerance in the mother. for example (pre)eclampsia. we still don't know WTF is going on exactly (but it's basically abnormal blood vessel forma

lack of immune tolerance in the mother. for example (pre)eclampsia. we still don't know WTF is going on exactly (but it's basically abnormal blood vessel formation between the fetus and the uterus), and a few decades ago it was basically guaranteed loss of the fetus or the mother (or both), in about half a percent of pregnancies. nowadays thanks to medical science it's a hundred-times more manageable.