Nytimes on pregnancy's effect on the female body. Sometimes after giving birth to boys there are cells from the kid which may haem and other times may benefit the mom. There'sa lot that is not understood.

"This biological tension might help explain how fetal microchimerism sometimes causes harm to a mother. It may simply be an occasional side effect of the cells’ manipulations.

There are some clues that mothers, too, pull hard in this evolutionary tug-of-war. The immune system kicks into high gear after giving birth, possibly to clear away leftover fetal cells. This defense may pose its own risks: Women with autoimmune disorders such as rheumatoid arthritis can suffer relapses after pregnancy."

http://nytimes.com/2015/09/15/science/a-pregnancy-souvenir-cells-that-are-not-your-own.html?referrer=



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