That Explains It

One of my favorite blogs -- duly listed off to the right -- is The Well-Timed Period. I've actually given patients the URL and sent them there for a fuller discussion of continuous contraception than I have time to review in the office.

Today's post links to some anti-abortion propaganda that was so outrageous, I found myself laughing out loud.

Finally! A scientific explanation for "mother's intuition":

The phenomena [sic] is called “human microchimerism”. Early in the pregnancy an exchange of cells begins between mother and child. We are not positive what the means of cellular exchange is, but we know it happens. At the time that the child leaves the mother’s body, whether as the result of an abortion, a miscarriage, a cesearean section or a vaginal delivery, even more cells are sent to the mother. It also seems that if the pregnancy ends early, an even greater number is transferred.

These cells seem to be some type of stem cell and are stored in the medulla of the mother’s brain—where instinct lies, but also throughout her body. They have been found even 37 years later so they appear to be replacing themselves.

Wow. That's pretty cool. I knew that red blood cells can cross the placenta, thus causing problems like Rh sensitization with an Rh negative woman and an Rh positive baby, but RBC's don't last more than about four months. (And they can't replace themselves, because they don't have nuclei.) Besides, there isn't any actual blood circulating until at least 6 weeks into the pregnancy.

But actual cells from every child ever conceived lodging throughout the mother's body? And in the medulla of the brain, no less, "where instinct lies." (I didn't realize "instinct" had been defined neuroanatomically.)

Let's think about this for a moment.

By definition, these cells are from another person; a unique individual with his or her own unique DNA. Even though half of it derives from the mother, half does not. The resulting combination is what makes people more than clones of their parents. Because of this foreign DNA, the maternal immune system must see these cells as invaders and thus it would be expected that they would be ruthlessly sought out and destroyed, as is the function of the immune system.

What would happen if these cells somehow managed not only to evade the immune system, but continued to "replace themselves"? There's actually a term for this when the cells involved are bacterial: it's called a "resistant infection." It seems reasonable to suppose that cells with foreign DNA which continue to replace themselves while evading the immune system could be called a form of cancer.

Therefore one of the causes of cancer in women who have ever been pregnant is most likely these cells from every child she has ever conceived that have somehow passed into her body. (I'm still trying to figure out why a shorter duration of gestation should result in more cells being transferred. I shall leave that as an intellectual exercise for the reader.)

But this conclusion should come as no surprise. It demonstrates a universal truth that every mother knows all too well:

Your kids make you sick.