Photo by Rick Geary

A UCSD scientist camped out at the San Diego Zoo looking for signs of queasiness among pregnant apes.

Dear Matthew Alice: The term “morning sickness” seems a misnomer in my wife’s case. During her pregnancy she was in terrible misery 24 hours a day for months, despite her careful efforts in following medical advice. It was like being constantly seasick with no end in sight. Her doctors were unable to tell her what causes such sickness. Do you have an answer? Also, I’ve never heard of animals other than humans suffering like this during pregnancy. Are other animals prone to such problems? — R.A., San Diego

Let me assure you I’m hoarding no secret knowledge on the subject, unwilling to share it with the medical community. The cause of morning sickness is long on speculation, short on scientific proof. Your second question is a lot easier. Just a year ago, a UCSD scientist camped out at the San Diego Zoo looking for signs of queasiness among pregnant great apes, our nearest genetic neighbors. None were seen. And no signs of morning sickness have ever been found in lower animals. Apparently it is an affliction reserved for humans.

Even a decade ago, the medical community suspected morning sickness (like other “female complaints”) was basically an emotional problem — anxiety or subconscious rejection of the pregnancy, perhaps. The fact that 75 percent of pregnant women experience some degree of nausea and vomiting (2 percent require hospitalization) does seem to argue against the idea that “It’s All in Your Head.” Speculation now is that increased estrogen is the culprit. Estrogen heightens the sense of smell, and this hypersensitivity triggers nausea and vomiting. Individual variations in body chemistry account for the degree of severity of the sickness and the diversity of the smell triggers. Scientific studies haven’t confirmed this conclusion, but it’s still offered as a possible explanation. Pregnancy also dramatically slows the digestive process, so this is also being investigated. Alternative theories: thyroid malfunction; deficiencies in zinc, copper, Vitamin B6; or biochemical changes resulting from the struggle for survival between mother and fetus.

This last theory, proposed by some evolutionary biologists, views pregnancy less as a cooperative venture than as subtle Darwinian chemical warfare, in which the fetus protects itself against miscarriage by inducing changes in the mother’s body. These changes perhaps trigger morning sickness, high blood pressure, diabetes-like symptoms, and other maladies in pregnant women.

But the newest evolutionary theory comes from maverick Margie Profet (degrees in political philosophy and physics from Harvard and Berkeley, once employed in a Berkeley biology lab, now “thinking” full-time on a MacArthur fellowship). As Profet explains it, the first trimester, when morning sickness is usually at its worst, is the time the developing embryo is most susceptible to toxins that cause serious birth defects. All body systems and structures are being established in a process of cell differentiation at this time. Morning sickness is the mother’s body sensing and rejecting potentially harmful substances. Profet speculates that the brainstem structure responsible for sampling blood for toxins may be “recalibrated” during the first three months of pregnancy, thus protecting the developing embryo. During the second and third trimesters, when nutritional requirements of the rapidly growing fetus take priority and susceptibility to toxins is lower, mom can pig out. According to Profet, it’s not by chance that bitter, spicy, and pungent foods are most commonly shunned by pregnant women. It’s the natural toxins in these foods that give them their characteristic flavors and smells. Profet is a “philosopher,” not a lab scientist, so it’s left to others to put her theories to the test.

Treatment of morning sickness with medications is risky business. One nontoxic antinausea remedy marketed to boaters and expectant mothers consists of an elastic band with a metal ball that is placed over the P-6 or Neiguan acupressure point near the wrist. Some people say it works.