Pregnancy is a state of constant physiological compensation, processes that simultaneously account for the physical needs of both mother and foetus. These changes create a complex and continuously evolving environment, one which depends on essential elements for continued optimal function. While these processes are vital to the maintenance of pregnancy, they are also pivotal to parturition, a process which relies on the actions of numerous micronutrients for essential endocrine and inflammatory pathways. As such, proper maternal nutrition is pivotal to optimal birth outcomes. Global, national and state agencies address nutrition within theoretical and conceptual frameworks; these interact with governance, clinical, and consumer factors to create complexities individuals must navigate when making nutrition-related decisions. This decision-making becomes more complicated during pregnancy due to social influences, such as advertising and peer pressure, and cultural factors such as food avoidance, traditions and beliefs. The confluence of these determinants influences each woman’s nutrition state, with the potential to result in transgenerational health consequences. Malnutrition is associated with suboptimal perinatal outcomes, a situation not restricted to low and middle-income countries. Although outcomes in these regions have improved with supplement interventions, research is yet to determine the efficacy of supplementation in high-income countries. However, despite the lack of evidence surrounding their safety and efficacy, and recommendations relating to the use of supplements during pregnancy, the pregnancy supplement market is estimated to reach a value of $673.8 million by the year 2025. This quantitative research explored data collected from three cross-sectional cohorts in order to explore the associations between micronutrient supplementation and birth outcomes in South-East Queensland women. The first of these datasets – the Environments for Healthy Living cohort - was a longitudinal birth cohort study with self-reported perinatal data collection undertaken between 2006 and 2011. The second was the Gold Coast Health and Hospital Service Maternity Information System cohort; a clinician controlled digital perinatal database with data available from 2014 to 2017. The third was the Maternal Outcomes and Nutrition Tool database, a cohort recruited explicitly for this study between 2016 and 2018, self-declaring data using a specially designed digital data collection tool. Collectively, these three cohorts examine the relationships between demographics, socio-cultural factors, micronutrition status, supplement use, dietary decision-making and their influence on the birth outcomes of 9300 women from South-East Queensland over the twelve years from 2006 to 2018. Six research aims informed three formative enquiries addressing the central research question. These aims examined evidence informing current recommendations regarding micronutrient supplements during pregnancy in Australia, determined if evidence of benefit exists regarding micronutrient supplements and birth outcomes in South-East Queensland women and explored the human factors affecting nutrition-related decision making in the study population. This research aimed to determine relationships between socio-cultural determinants of health, micronutrition, supplement use and birth outcomes in pregnant women of South-East Queensland. A literature review was conducted, highlighting current limitations and knowledge gaps relating to the influence of supplementation in nutritionally replete and high-income populations. Furthermore, current data collections were found to exhibit significant limitations inhibiting accurate determination of causal relationships. As such evidence informing current recommendations during pregnancy was determined to be neither robust nor contemporary. Driving dietary decision making were several social, health, cultural and economic factors. These include smoking, income, education, cultural and linguistic diversity, access to maternity care models, the range of maternity care models and providers, and health service resources. In particular, women from low-socioeconomic backgrounds - including women who smoke and women from cultural and linguistically diverse backgrounds - reported nutrition motives that position health factors as a low priority. While these women did not demonstrate evidence of benefit from micronutrient supplements, they did declare nutrition decision-making behaviours that would benefit from dietary counselling and support strategies. The synthesis of information afforded by this research has determined that micronutrient supplementation is not appropriate in pregnant women of South-East Queensland. Further, supplementation did not improve birth outcomes in either the general population or in women from demographic groups considered to be at risk for suboptimal outcomes. Conversely, non-therapeutic use demonstrated the capacity for detrimental effects across all three cohorts, particularly concerning the effect of micronutrient supplements on overweight women and the incidence of prolonged pregnancy. Determination of what constitutes sustainable, safe and effective nutrition interventions in women at risk of suboptimal birth outcomes requires further empirical research.