The effectiveness of informed consent in the widespread community education was evaluated in a randomized controlled trial, using periconceptional vitamin supplement to prevent spina bifida and anencephaly in Mancheng County, Hebei Province. Results showed that 60% and 70% of women in the pre-education group knew the terms of "vitamin" and "birth defects", but the proportions of women who had ever heard of the terms of "spina bifida", "anencephaly", and "neural tube defects" were rather low. No woman had any knewledge of "folic acid". In the post-education group, there was not much change in the proportions of women who knew the terms of "vitamin" and "birth defects". Women with less knowledge at the pre-education group increased their knowledge more obviously: 12% of the women who knew folic acid and the maximum levels of other three items were about 2-13 times of the pre-education group which reached about 40% -50%. Women showed strong ability of receiving new knowledge and the education campaign seemed effective in the widespread community to a large extent.