Introduction: Histogenesis of the fetal cerebrum can be useful in the treatment of Lisencephaly, Cerebral hypoplasia, Polymicrogyria and heterotopias which are sex-linked inherited disorders using the Targeted Drug Delivery system by Nanoparticles in in-utero in future. In the present study, we had measured the thickness of the cortical plate of the motor area in micrometre using Image J software. Aim: To study the thickness and number of layers in the primary motor area of the fetal cerebrum in different gestational ages. Material and Methods: Hundred cerebral hemispheres obtained from 50 fetal cerebrums were collected. These brains were obtained from fetuses ranging from the 17th week to the 40th week. The study was authorized by the Ethical Committee for Analysis of Research Projects. Cortical thickness of the motor area of both sides of the cerebrum was measured by Image J software after doing routine H __ampersandsignamp; E stains. The number of layers was identified in different gestational ages of human fetuses. Results: The cortical thickness of the right motor area from 17th week to 40th week was 106.83 - 2298.19 micrometre and the left motor areas were from 111.14 __ampersandsignndash; 2330.37 micrometre. At the 17th week, 3 layers were observed. 20th week 4 layers were observed, 22nd week 5 layers were observed and from 24th week onwards all the 6 layers were observed. Conclusion: The number of layers and cortical thickness increases with the increasing gestational age. By birth, the cerebral cortical thickness is approximately 2 mm.