There is increasing awareness that consuming a low glycaemic index (GI) diet during pregnancy may have beneficial effects on pregnancy outcomes. A low GI diet will reduce postprandial glucose excursions and incidentally increase the fibre content. However, in many instances lower GI food choices can be more expensive than their more ubiquitous but higher GI equivalents. This has led to the perception that following a low GI diet may be more expensive and this perceived higher cost may be a disincentive to follow the diet. The aim of this study was to examine the monetary cost of dietary change among pregnant women before and after receiving low GI dietary advice. The pregnant women in this study were participants in the PREGGIO (Pregnancy and Glycaemic Index Outcomes) study. Twenty women were randomly chosen from the 85 women in the low GI dietary advice group who had completed their pregnancies. All these women had completed three day food records at 12-16 weeks and again around 36 weeks of gestation. Consumer food prices were determined from a supermarket chain in a major regional city in August 2011. The recorded prices of the foods obtained on the day were then applied to the participant’s dietary intake data and the daily cost of the diet was calculated. The mean ± SD GI of the diet reduced from 55.1 ± 4.3 to 51.6 ± 3.9 (p = 0.003). The daily cost of the diet (AUD$) was 9.1 ± 2.7 at enrolment and 9.5 ± 2.1 prior to delivery (p = 0.52). Women were able to follow low GI dietary advice during pregnancy without an increase in costs. The use of low GI and low cost foods like dairy produce, pulses and pasta, for example, are likely to have offset the additional costs of substituting equivalent foods, like grain breads compared with white breads.