BACKGROUND: It is a common opinion that expansion and darkening in melanocytic nevi may occur during pregnancy. The main problem is that whether it is a usual finding, or it is a condition that requires suspicion about melanoma. OBJECTIVES: It was aimed to find the changes that might occur in the sizes and structures of melanocytic nevi during pregnancy. METHODS: Ninety-seven nevi of the 56 pregnant women in the first trimester were evaluated in the study. The localization and size of the nevi were recorded on a standard body diagram. After clinical examination, dermoscopic analyses were applied. Pattern analyses were done, and total dermoscopy scores (TDS) were calculated by applying ABCD scoring system. All subjects were seen again during the third trimester. RESULTS: There was a statistically significant difference between the mean diameters of nevi in the first and third trimester (P = 0.001). Of nevi whose diameters increased, 10 (50.00%) were localized on the front of body, 6 (30.00%) on the face and neck, 3 (15.00%) on the legs, and 1 (5.00%) on the back. The enlargement in diameters was more significant on the front of the body, but there was no statistically significant difference. Compared according to the pattern analysis, new dot formation was observed only on the structure of six nevi during the last trimester. Four of them were localized on the front of the body. There was statistically significant increase in mean TDS in comparison between the first and third trimesters (P = 0008). CONCLUSIONS: During the pregnancy, widening in diameters and structure changes of nevi may be seen especially on the front of the body. We also think that these findings might be connected with expansion of the skin during pregnancy. Dermoscopic controls are the first choice of method to analyse the nevi since the patient may not recognize these changes.