Tuesday, March 14, 2006

A Different Take on the Maternal-Fetal Conflict in Pregancy

Women know that pregnancy can be wonderful, and that it can also be dangerous: Around the world, an estimated 529,000 women a year die during pregnancy or childbirth and roughly ten million suffer injuries, infection or disability. David Haig, an evolutionary biologist at Harvard, notes that while pregnancy is absolutely central to reproduction, it doesn't seem to work very well -- that pregnancy is associated with all sorts of medical problems. Why? Dr. Haig argues, a mother and her unborn child engage in an unconscious struggle over the nutrients she will provide it.

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.

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