The standard explanation for morning sickness is that it’s an evolutionary response to potentially harmful foods and toxins. Between approximately weeks 5-13—when the embryo is most vulnerable– women suddenly become extremely smell-sensitive and prone to being grossed out or otherwise nauseated.
But not everyone gets morning sickness. And some women are repulsed by perfectly healthy foods and crave suspicious ones. While there are ways to explain these variations, there’s one guy who has entirely different explanation for morning sickness and it has a lot to do with sex and semen.
So much so that he reckons more sex in the first trimester might help quell the nausea. Or even just lots of blow-jobs.
Let me explain:
In a fascinating history of the science of morning sickness in Slate this week, Jesse Bering looks at the work of SUNY Albany psychologist Gordon Gallup who discovered that women who are impregnated with unfamiliar semen — from a sperm donor, say — are more likely to develop preeclampsia than those who are impregnated with familiar semen — from a long-term relationship where condoms were not frequently used, for example.
Gallup wonders if precclampsia, a serious condition some women get after 20 weeks of pregnancy that can cause seizures and requires immediate delivery of the baby, might be a kind of tweaked immune response from the mother’s body to the DNA carried in the fetus.
Mom’s immune system is suppressed in early pregnancy so that her body will not treat the embryo (which is half dad’s DNA) as foreign matter or an infection. Perhaps preeclampsia (which we don’t fully understand) is a kind of tweaked immune response. When Gallup found lower rates of preeclampsia in women who were exposed to lots of the father’s semen, even via oral sex and swallowing, baby daddies rejoiced.
Now he’s speculating that perhaps morning sickness is the expression of mom’s immune response to dad’s DNA in her body. The more mom has been exposed to dad’s DNA via sperm, the lower her symptoms might be. His theory is untested but he thinks if tests are done we’ll see that women with little exposure to the father’s sperm will have more severe morning sickness than women who have had lots of exposure. If he’s right it might mean that more sex you have (while trying not to vomit) the faster the nausea will subside. Bering explains:
“Gallup surmises that pregnancy sickness is … a side effect of a broader maternal adaptation for favoring the best possible mates. He suggests that this broader adaptation serves primarily to facilitate reproduction with males that are likely to support mother and child (in evolutionary terms, to invest in the offspring), while weeding out the players. In previous work, Gallup has shown that women are more likely to develop preeclampsia—and thus have a higher infant mortality risk—in pregnancies resulting from unfamiliar semen. Historically, these would have included rape and ‘dishonest mating strategies’ (tactics in which the man lies to the woman about his long-term intentions just to get into her pants) as well as unplanned conception occurring in a new, still-fragile relationship. From the point of view of Mother Nature’s cold, cold heart, spontaneous abortions due to a reaction against unfamiliar semen might have been biologically adaptive. This is because conception and childbirth historically meant that a woman foreclosed on any other reproductive opportunities for 2 to 4 years, so pregnancies in which paternal investment was improbable would have meant an enormous gamble.”
I am actually very intrigued by the idea that mom’s body may be making calculations– based on DNA, or maybe even dad’s bacteria, I wonder– about whether the father is going to stick around long enough to make this all worthwhile. But how much of our culture are we projecting on to biology? This theory presupposes the importance of the father for child-rearing. There are other cultures where mothers rely on their own families, or the proverbial “village,” for the lion’s share of childcare/support. And many cultures where women have very little exposure to a guy’s semen before sex/impregnating.
I also think that we’ve got some pretty compelling research about how a mother’s instincts become very protective in the first trimester. One study showed that moms become more suspicious of not just weird foods but other races when pregnant– researchers wonder whether this xenophobia might be an evolutionary response to fear of “outsiders” who may bring unfamiliar bacteria. So interesting! Plus, nausea and vomiting in early pregnancy is correlated with a slightly lower risk of miscarriage making it seem essential or at least useful in some (evolutionary) way.
Gallup announced at the 2012 meeting of the Northeastern Evolutionary Psychology Society in Plymouth, N.H, is going to test his hypothesis to see if semen exposure does in fact correlate with morning sickness severity.
But ladies, do we really need to wait for this guy’s study to be completed? I think we can get to the bottom of this theory right here in the comments section. Sperm exposure? Morning sickness severity? Chime in.
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