EN
The studies were performed on 2060 coldblood and 195 English half-blood mares. On the basis of the shape of foetal vesicles and their organization, eight subperiods were distinguished in the first 90 days of pregnancy. Some deviations in the typical pictures of the vesicles during the subperiods were found. They were associated with the size and shape of vesicles which in turn might be the signs of approaching foetus resorption.