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The big story today: A new study from the University of Liverpool found that birth control pills could be messing with women’s ability to find genetically dissimilar partners, thereby upping the chances of infertility, miscarriage, and offspring with weakened immune systems.

The key issue, according to Craig Roberts, an evolutionary psychologist who led the study, is body odor:

Humans choose partners through their body odor and tend to be attracted to those with a dissimilar genetic make-up to themselves, maintaining genetic diversity. Genes in the Major Histocompatibility Complex (MHC), which helps build the proteins involved in the body’s immune response, also play a prominent role in odor through interaction with skin bacteria. In this way these genes also help determine which individuals find us attractive.

The pill has been shown to affect the sense of smell in the past, and while the exact reason for this side effect isn’t known, researchers have speculated that, since the areas of the brain that control both the sense of smell and the ovaries are located near one another, taking a pill that alters one could alter both.

The problem with the odor effect, argue the authors, is that it alters subjects’ preferences for genetically dissimilar men—a loaded idea, given that it hints there might be serious repercussions from the world’s most popular form of birth control. The odor-changing theory has been around for a while, and until now most of the data on MHC differences were gathered from rodents.

So Roberts and his team decided to take their hypothesis to human subjects, asking 100 women to sniff six different male body odor samples both before they started taking the pill, and then again a few months later, after they started taking it. Sure enough, the subjects demonstrated the same change in preferences as the mice.

So should we tell the millions of women on the pill to throw their prescriptions away? Not so fast. Several studies looking at tens of thousands of women have found no link between infertility or miscarriage and pill use. But as an added kicker, Roberts asserts that oral contraception could “ultimately lead to the breakdown of relationships” after women stop taking it, since “odor perception plays a significant role in maintaining attraction to partners.”

But in a tiny sliver of good news, at least it probably won’t be reclassified as abortion.

August 13th, 2008 Tags: abortion, contraception
by Melissa Lafsky in Health Care | 7 comments | RSS feed | Trackback >