In a 1993 paper, Dr. Haig first predicted that many complications of pregnancy would turn out to be produced by this conflict. One of the most common complications is pre-eclampsia, in which women experience dangerously high blood pressure late in pregnancy. For decades scientists have puzzled over pre-eclampsia, which occurs in about 6 percent of pregnancies.Dr. Haig proposed that pre-eclampsia was just an extreme form of a strategy used by fetuses, somehow raising the blood pressure of their mothers so as to drive more blood into the relatively low-pressure placenta.
Dr. Haig says that people seem to think that he must have a political agenda, but he explains that he's not talking at all about conscious behaviors -- he's just interested in these mechanisms and why they evolved.