Thesis title: Dietary behaviour during pregnancy, subsistence patterns and obstetric dilemma: an evolutionary perspective
The present dissertation includes two studies which focus on an evolutionary perspective on antenatal dietary behaviour, in particular culturally-induced food restrictions, across subsistence strategies. The first research (indicated as “Part I” in the dissertation, currently on peer-review) is a meta-analysis on cross-cultural food taboos during pregnancy across agricultural and non-agricultural societies. The main result is the major avoidance of carbohydrate staples due to concern over increased birthweight and difficult delivery among agriculturalists, while non-agriculturalists tend to have less foods restrictions overall and more addressed to animal products for non-physiologic motivations. This result was in line with growing evidence of agricultural diet as possible exacerbating factor for obstructed labour and therefore obstetric dilemma. Given the important possible implications for both public health and evolutionary research, the study merged into a fieldwork about antenatal food avoidance between agriculturalists and fishers in Madagascar, which was supported the National Geographic Early Career Grant in 2018. The results (illustrated in “Part II”) confirmed at a population and quantitative level what was found cross-culturally in literature. The concern over increased infant size attributed to carbohydrate staple crops resulted to be the main driver of antenatal food restrictions in Madagascar, therefore being more present among agriculturalists. The rate of obstructed labour is indeed high in Madagascar, confirming that cultural norms which regulate dietary behaviour during sensitive life stages are not independent from biological factors. However, it is likely that reduced stature and pelvic dimensions due to malnutrition and non-diversified carbohydrate-rich diet, rather than high infant birthweight in the strict sense, are the main determinants of obstructed labour in Madagascar. Future research should: i) create regional datasets on infant birthweight, maternal nutritional status and stature, and obstructed labour in Madagascar, as well as food composition tables for local staple crops; ii) apply the growing evidence of a relation between carbohydrate consumption, stature and obstructed labour to produce proxies of past maternal mortality in the human remains record.