Most women have heard about the common side effects of hormonal birth control. Whether they’re horror stories relayed by roommates about dramatic weight gain or tales of triumph from friends about miraculous acne disappearance or (gasp!) four periods a year, you’ve probably heard them all by now.
But all of those sometimes pleasant, sometimes infuriating side effects brought on by hormonal birth control are boring next to those that recent research has (possibly) uncovered. Two studies in particular have garnered a fair amount of press in recent years–and for good reason. They suggest that a lot of how we feel about our romantic partners is determined by hormonal birth control methods. As one half of a happy, long-term couple, the question immediately rose unbidden in the back of my mind—am I being tricked by my birth control?
Hormonal birth control works by essentially tricking the body into thinking it is pregnant. It artificially holds the cycle at the point before ovulation, so that the woman never ovulates. The theory states that because of this arrest, our “natural” preferences, based on hormone levels, are altered.
One study, outlined in Trends in Ecology and Evolution, suggests that women who do not take oral contraceptives experience an increased desire for more masculine, symmetrical-looking men during mid-cycle (ovulation). In evolutionary terms, they are looking for a short-term mate with the potential for fathering children with strong immune systems. In reality-show terms, they are looking for hunky baby daddies. Apparently, however, women on the pill do not experience this change in preference to the same extent.
Another study, published by the Proceedings of Royal Society B in 2008, discusses the major histocompatibility complex (MHC) and its effect on mate selection. The MHC is involved in cell signaling—a kind of signpost on cells that indicate whether the cells are “self” or “nonself.” Olfactory complexes help women (and other female animals) determine if a potential mate has a similar or dissimilar MHC complex. MHC-dissimilar mates are ideal as they increase genetic diversity and immune strength in children produced from the pairing. In the experiment by the Royal Society, women were asked to smell t-shirts that had been slept in by men for two nights. They smelled them both when they were not on hormonal birth control and when they had been taking the pill for several weeks. Unlike in previous studies, the women did not show particular preference for MHC-dissimilar men when they were not on birth control. However, they did show a marked preference for MHC-similar men when they were on the pill, in comparison to the control group, whose preferences did not significantly differ.
Evolutionarily speaking, the theory goes that women look for men with diverse genes (MHC-dissimilar) when they are ovulating and looking to reproduce. But when they are pregnant (or when their bodies are tricked into thinking that they are) they look for MHC-similar men that are potentially related and are more likely to be more nurturing to them and their children.
I sat down with Science in Society Professor Laura Grabel, a stem-cell aficionado and all around amazing person, to discuss the validity of these studies and their possible ramifications. She said that she didn’t place a lot of stock in the masculinity study.
“I’m particularly concerned about ‘how virile your mate is,’ because I don’t know how you can objectively define or quantify these things,” she said. “I understand that these studies are difficult to do, and I would want to look at the data very critically.”
She also said that, although there are theories behind the causes for the results of these studies, the hormone levels and the specific hormones that are causing the changes haven’t been tested.
“They’re inferring from women who are taking birth control pills,” she said, “So we don’t really know what the direct hormonal cause is. It could be a secondary effect. It could be that estrogen is doing something else that in turn is affecting this.”
She also cautioned against putting too much faith in one study.
“In and unto themselves, they’re each one single study. You always want to see that things like this are supported by additional data before you assume that they’re the absolute truth.”
Though she says that the MHC studies are more straightforward and are therefore probably more significant, she says that she doesn’t know what it means long term.
“Should it alter a woman’s decisions about method of birth control? I don’t think so,” she said. “Your choice of your lifelong partner is going to be dependent on many, many things.”
So yes, it’s possible that your birth control may be “tricking you” in a very limited respect. But, like all decisions, those regarding sexual health are all about weighing the pros and cons. I know that I love and am attracted to my boyfriend for reasons other than his MHC similarity or dissimilarity to me. And for me, the ability to choose when I will have children (with four periods a year to boot!) is more important than birth control’s potential hormonal side effects.
Francis is a member of the class of 2014.