One of the best things about being a gay man is that one doesn’t have to worry about accidentally impregnating his partner, or, for that matter, getting knocked up. That’s probably a good thing in my case, since I have a very low tolerance for any form of pain and discomfort (except the good kind) and such inconveniences tend to go along with the long, tumultuous gestation of a human conceptus gathering mercilessly inside a woman’s abdominal cavity. It’s all very wonderful bearing a child, I’m sure, and life-affirming; but on the other hand, one of the worst parts of being pregnant—and I was informed concretely of this very fact by some vomitus landing on my sandaled foot—is what is commonly referred to as morning sickness.
This term for the nausea and vomiting accompanying pregnancy is something of a misnomer, actually, since such gastrointestinal issues certainly aren’t limited to the morning hours. Rather, for those women who do get green around the gills (and not all do; more on that later) sudden bouts of toilet-hugging can happen morning, noon and night. But much as mild fevers may help boil away bacterial infections, some degree of nausea and vomiting, at least during the early stages of pregnancy, may be helpful and adaptive—an evolved mechanism that protects both the fetus and mother.
One of the first to notice the salubrious effects of this “pernicious vomiting of pregnancy” was a Boston-based physician named Frederick Irving. In 1940, Irving reported that women in his clinic who experienced strong food aversions early in their pregnancies were less likely to suffer miscarriages than were women whose first trimesters were easier to stomach.
In 1976, Ernest Hook, an endocrinologist at Albany Medical College, postulated a functional theory of the condition, suggesting that nausea and vomiting protected the developing fetus from foods that could compromise its anatomical development. In embryological jargon, elements that can cause mutations early in development are known as teratogens; these can be any of a host of things—with Chernobyl-level radiation being an extreme example—but they include caffeinated beverages, tobacco, and alcohol, and these are the types of items that Hook focused his attention on. Many pregnant women exhibit an aversion to these products, he pointed out, particularly during the crucial first trimester when the fetus’s basic body plan (limbs, appendages, digits, and other things that make us look like standard-issue human beings) is particularly vulnerable to deleterious foreign substances invading the womb. Such teratogens can be avoided by nausea or expelled by vomiting.
A proper evolutionary accounting of pregnancy sickness was formulated in 1992, when the biologist Margie Profet articulated the compelling argument that it is an intricate adaptive mechanism. (Profet, who was awarded a MacArthur “genius grant” in 1993, was in the news recently for emerging after a long and mysterious absence.) She noted that, while teratogenic goodies like absinthe and mocha lattes weren’t exactly a threat to our pregnant ancestors in the African savannas hundreds of thousands of years ago, such products do have high concentrations of so-called secondary plant compounds. These phytochemicals deter or kill plant enemies such as insects, fungi, and bacteria. They’re usually harmless to humans, but when consumed in large quantities, they can be allergens, carcinogens, mutagens and, in pregnant women, teratogens and even abortion-inducing agents.
Animal products also would have posed dietary problems for our ancestral mothers. Meat is a perfect hiding place for dangerous microorganisms. Salmonella, for example, thrive in eggs, and roundworms can inhabit seafood. Toxoplasma gondii, which can be found in raw or undercooked meat and, notoriously, in cat feces (which hopefully you’re not snacking on even when you’re not pregnant), has been linked to spontaneous abortions, congenital brain defects, and even schizophrenia.
Not only does nausea and vomiting shield the developing embryo from toxins, Profet reasoned, but these responses may also protect the mother. Her immunological defenses are lowered during pregnancy, especially during the first trimester, which allows her to accommodate the half-foreign genome of the lovely little beast incubating in her womb. If her immune system operated at full speed, it might reject the fetus. By avoiding certain foods, she simultaneously decreases the risk of her offspring’s exposure to teratogens while protecting herself from those toxins and parasites that she is in no shape to fight.