Adequate maternal health and nutrition have long been considered important to a healthy pregnancy, with use of a pregnancy specific multivitamin widely recommended to prevent disorders such as neural tube defects and support the maternal system manage the stresses of pregnancy. Recent cohort studies have suggested that the use of multivitamins during pregnancy may significantly reduce the risk of preeclampsia, preterm delivery, gestational diabetes and improve pregnancy outcomes. To date there have been no published studies reporting the effect of supplementation across the course of pregnancy especially in the third trimester. Analysis of the effect of multivitamin use on outcomes of pregnancy was conducted using data collected as part of the Environments for Healthy Living Project, Griffith University that holds data from a total of 2619 live births that took place between 2006–2011 in the South East Queensland region. In this cohort multivitamin use was most significant in the first trimester (57.5%) however 37% of the population reported supplement use at any time throughout gestation. Analysis of this cohort revealed first trimester associations between supplementation and reduced incidence of preeclampsia and preterm delivery. The benefits of supplementation however was found to be limited to early gestation with third trimester multiple micronutrient supplementation associated with increased risk of prolonged pregnancy and significantly greater rates of inductions of labour and birth complications. The results of this study support the hypothesis that multivitamin supplementation may be beneficial during early pregnancy however suggests that this beneficial effect diminishes as parturition approaches. Further investigation of this effect is warranted to support women to make informed choices about supplement use and to support health care practitioner to provide adequate nutritional counselling during pregnancy.