For most women, morning sickness during pregnancy is simply a part of the baby making process, much like choosing the perfect name and readying that beautiful nursery, and yet it is only recently that scientists have been able to pinpoint the potential cause.
There are many misconceptions around the unpleasant morning sickness that is experienced by pregnant women. Some dismiss it as “hormonal” while others feel that it chooses would-be mothers at random. An important new UCLA study has quashed these notions however, revealing that this difficult aspect of being pregnant may actually be a useful and natural immune response.
According to the National Institute of Health, up to 80% of pregnant mothers experience some nausea during the early stages, leading to vomiting and strong aversions to specific foods and smells. Experts now suggest that despite the dreaded symptoms, this phenomenon has actually evolved to protect baby and mother. “During pregnancy, a mother’s immune system faces a tricky challenge,” explains UCLA anthropology professor Molly Fox, who served as a corresponding author on the breakthrough study. “It has to protect both her and the fetus from infection, but without accidentally attacking the fetus, whose genetic identity is half-foreign because it is half derived from the father. Normally, the immune system attacks anything that seems foreign, so in pregnancy, it has to carefully adjust to keep the fetus safe while still defending against infection.”
How Was the Study Carried Out?
The UCLA-led team analyzed the blood samples of 58 Latina women in Southern California, who were observed from early pregnancy through to postpartum. One of the primary purposes of the study was to measure immune system molecules called ‘cytokines.’ These are proteins that send signals to help the body launch a quick defence against sickness while regulating inflammation. Participants were also asked to fill out questionnaires that asked about their morning sickness-related symptoms, along with their food and smell aversions during the early stages of pregnancy.
What Were the Results?
Once crunched, the data showed that 64% of the study’s participants experienced odor or food aversions, with primary triggers being tobacco smoke and meat. The women who experienced an aversion to tobacco smoke also showed a heightened inflammatory response. This correlation is consistent with the researchers’ theory: that these symptoms may be part of an evolutionary adaptation that helps pregnant mothers’ bodies to minimize their exposure to harmful substances.
UCLA cautions that the evidence is not yet definitive and more research is needed on a larger sample size to confirm their results, but why do humans suffer morning sickness when other mammals get off Scot-Free? “In many mammals, the fetal compartment has barriers separating it from the mother’s blood supply, where her immune cells are,” explains Fox. “But in humans, we have a unique setup — fetal cells are bathed in maternal blood. Humans have the most invasive of all placentas, burrowing deep into maternal tissue. So, humans need unique strategies to prevent the mother’s immune system from attacking the fetus.”
Those immunological changes are what may induce nausea, which in turn encourages food avoidance as a potential additional layer of protection. “Nowadays, you will see labels on packages of ground beef or soft cheese that warn pregnant women to be cautious about these products because of the risks of foodborne illness during pregnancy,” notes Professor Daniel Fessler, who also served as a co-author on the new study. “Aversions to certain odors and foods, and nausea and even vomiting, appear to be evolution’s way of achieving that same objective.”
The researchers hope that the information found in this study could help bolster recognition that nausea and vomiting are normal symptoms with biological underpinnings associated with healthy pregnancies, while the results could help in paving the way for common-sense workplace accommodations, placing pregnant mother’s away from morning sickness triggers where possible.
