Objectives This study explored nutrition knowledge of pregnant women, and how it correlated with participant characteristics, their main sources of information and changes to their diet since becoming pregnant. Methods Pregnant women residing in Australia accessing pregnancy forums on the internet were invited to complete a web-based questionnaire on general nutrition and pregnancy-specific nutrition guidelines. Results Of the 165 eligible questionnaire responses, 114 were complete and included in the analysis. Pregnancy nutrition knowledge was associated with education (r s = 0.21, p < 0.05) and income (r s = 0.21, p < 0.05). Only 2 % of pregnant women achieved nutrition knowledge scores over 80 %. Few women received nutrition advice during their pregnancy, of which most were advised by their doctor. Dietary changes adopted since becoming pregnant included consuming more fruit, vegetables, dairy and high fibre foods. Conclusions for Practice Pregnant women in this study had limited knowledge of the dietary guidelines for healthy eating during pregnancy. Furthermore, nutrition counselling in maternity care appears to be infrequent. One approach to optimising maternal diets and subsequently preventing adverse health outcomes is to enhance their knowledge of the pregnancy nutrition guidelines through the provision of nutritional counselling. Furthermore, research exploring the access and use of nutrition resources, and nutrition advice provided to pregnant women is recommended to understand how knowledge impacts on dietary behaviour.