Purpose: We aimed to investigate maternal thyroid parenchymal vascularity with 2-dimensional color superb microvascular imaging vascularization index (2D-cSMIVI) levels and thyroid gland volume in the first, second and third trimesters. Methods: This longitudinal prospective study was carried out with participants selected from 30 healthy asymptomatic pregnant women. Ultrasonography (US) for the thyroid gland was performed in each trimester. The vascularization index (VI) values obtained by manually drawing the contours of the thyroid parenchyma in the longutidinal plane, using the free region of interest (ROI) with 2DcSMIVI mode. VI values obtained in each trimester, thyroid hormone levels (TSH, T3, T4) and thyroid volumes were compared. Results: We have detected that thyroid gland vascularity increased significantly as pregnancy progresses. The mean VI values of thyroid gland in third trimester were significantly higher than first and second trimester (p < 0.001), and the mean VI values of the thyroid gland in the second trimester were significantly higher than first trimester (p < 0.001). During pregnancy, we detected the increase in VI values, TSH levels and thyroid gland volumes. Conclusion: Maternal thyroid gland gray scale findings, parenchymal vascularization, thyroid volumes should be evaluated routinely for the healthy fetal development. 2D-cSMIVI method allows us to evaluate vascularization with quantitative numerical values objectively. We have detected that the VI values and volume of the thyroid gland increases as pregnancy progresses. In the complex situation of pregnancy process, the thyroid gland can be evaluated quantitatively with SMI method effectively.