The aim of the study was to assess the accuracy and readability of Internet prenatal nutrition advice. Between August and December 2018, 130 Internet pages returned from Google searches on foods to avoid, foods to eat and supplements use were compared with UK government advice for pregnant women. Readability was assessed using the Flesch Readability Ease (FRE) tool. Descriptive and non-parametric tests were used. Spearman’s correlation explored associations between accuracy and readability. Kruskal–Wallis tests with Bonferroni correction were used for multiple pairwise tests and Mann–Whitney U tests for two-sample differences in medians. A total of 130 Internet pages were examined: 48 % from publishers, 27 % from other commercial organisations, 22 % from charities and 3 % from governments. Eighty-three (64 %) pages contained inaccurate and accurate advice, twenty-three (18 %) were accurate and complete, twenty-one (16 %) were inaccurate, and three (2 %) lacked any relevant advice. The median percentage accuracy of all advice was 83 (lower quartile, upper quartile: 48, 100). Median FRE was 55 (46, 61) ‘fairly difficult’. Eighty-seven pages (67 %) scored below the recommended FRE for public Internet pages. There was a weak positive correlation between accuracy and readability of Internet pages (rho = 0·241, P = 0·006). Accuracy of Internet pages did not differ by dietary theme. Pages on supplements were the most difficult to read. Internet pages from publishers and other commercial organisations were significantly less accurate than those from not-for-profit organisations (median percentage difference –8 (–29, 0·00), P = 0·019). Much pregnancy-related dietary advice online is inaccurate and difficult to read. Advice should be developed in consultation with qualified nutritionists and dietitians.