The expression and adaptive significance of pregnancy-related nausea, vomiting, and aversions on Yasawa Island, Fiji

Abstract

We report a study on nausea and vomiting of pregnancy (NVP) and pregnancy-related food aversions in a small-scale society from Yasawa Island, Fiji. Because NVP has rarely been studied quantitatively in small-scale populations, we begin with a detailed description of its expression among the women of Yasawa. We found that 66% of these women experience nausea and/or vomiting in tandem with the development of aversions to certain foods. This pattern of expression is similar to what has been documented for industrialized populations, and the prevalence of 66% is close to the industrialized mean prevalence of 69%. We then use the data from the women of Yasawa to evaluate the three main hypotheses that have been put forward to explain the evolution and ecological function of NVP. We show that food aversions of pregnancy focus preferentially on food types that are more likely to carry pathogens or contain chemical toxins. Such aversions do not focus on nutrient-dense foods or on frequently encountered foods. These findings are most consistent with the hypothesis that NVP, along with pregnancy-related aversions, evolved to motivate women to avoid exposure to diseases and other toxins when they are immune-compromised by pregnancy and during a critical period of embryo development. These findings contribute to a growing body of theoretical and empirical literature that suggests that NVP symptoms represent a series of adaptations rather than pathological responses to the physiological demands of pregnancy.