<i>Introduction</i>: The placenta has drawn attention as an important indicator of intrauterine condition of fetus and maternal diseases. The study of number of cotyledons of placenta in different gestational age groups of healthy pregnant mother of Bangladesh is cross sectional descriptive study. <i>Aim of the study</i>: The aim of the study was to study the variation of number of cotyledons of placenta in deferent state of gestational ages of healthy pregnant mother. <i>Methods</i>: This cross sectional descriptive study was conducted in the Department of Anatomy, Mymensingh Medical College, Mymensingh, from January 2018 to December 2018. This study was performed on 80 human placentae. <i>Result</i>: The mean (± SD) number of cotyledon of the placenta was 18.56 (±2.15) in group A, 21.21 (±3.11) in group B and 23.75 (±3.45) in group C. The mean number of cotyledon of the placenta was maximum in group C (23.75) and was minimum in group A (18.56). It was also observed that the mean number of cotyledon of the placenta increased with gestational age. The mean difference of the number of placental cotyledons between groups A and C was statistically moderately significant (p < 0.05) but between A and B and B and C was statistically non-significant (p > 0.05). <i>Conclusion</i>: The placental examination becomes important as it will help in understanding the specific etiologies of adverse outcome. This study has shown that the mean number of cotyledon of the placenta increased with gestational age.