Based on data obtained from the system MoZMaD - PL (Polish Mother and Child Health Monitoring System); an equivalent of the American system PRAMS (Pregnancy Risk Assessment Monitoring System). The health behaviour of a pregnant woman, including adequate nutritional behaviours and supply of all the necessary nutrients, exert an effect on the health of a woman, development of the foetus, and the occurrence of diseases among the offspring at the age of maturity. The objective of the study was analysis of the nutritional behaviours among Polish pregnant women, with particular consideration of the recognition of dietary changes caused by the fact of becoming pregnant. The studies were based on questionnaire forms within the Polish Mother and Child Heath Monitoring System (MoZMaD - PL) implemented in Poland. The precise day of studies is appointed annually for the whole of Poland by the Chief Sanitary Inspector. The questionnaire forms were correctly completed in 2010 by 2,877 women. The replies to the questions were introduced by surveyors into the MoZMaD - PL system, a central database managed by the Institute of Agricultural Medicine. The results obtained were subjected to statistical analysis. More than a half of Polish women change their diet in pregnancy. According to the pregnant women examined, the changes in their diet consist in a more frequent consumption of white meat, fish, fruits and vegetables, as well as milk and dairy products. Favourable changes in diet were observed primarily among the respondents from the urban environment. Considering an insufficient awareness with respect to nutritional behaviours among females at reproductive age, the education of pregnant women and those who plan a pregnancy concerning an adequate diet should be jointly conducted by medical circles, schools, and the media, and directed primarily to women from the rural environment.