Objective:To measure the morphological parameters of the fetal vertebral centrum ossification centers (COC) in the second-third trimester using MRI susceptibility weighted imaging (SWI), and to explore the growth and development trajectory of the vertebrae.Methods:Fetus in the second-third trimester with normal vertebrae development were prospectively and continuously included in Shandong Provincial Hospital Affiliated to Shandong First Medical University from December 2015 to December 2021, and the SWI scanning of fetal spine was performed. The following morphometric parameters of the C4, T6, L3, S1 vertebrae COC were measured, including sagittal diameter, transverse diameter, height, cross-sectional area and volume. The linear and nonlinear regression analysis was used to derive the best-fit curve for each parameters and gestational age.Results:A total of 112 fetuses were recruited with gestatonal age 21-39 (29.4±3.9) weeks, including 30 cases of C4, 58 cases of T6, 92 cases of L3, 62 cases of S1. Fetal spine in utero with global curvature was kyphosis, presenting two primary curves (thoracic and sacral kyphosis). The morphological parameters sagittal diameter, transverse diameter, height, cross-sectional area and volume of C4 followed the quadratic polynomial rule during 25 to 38 weeks (R 2=0.938, 0.943, 0.952, 0.957, 0.982). During 21 to 38 weeks, the sagittal diameter, transverse diameter and height of the T6 followed the exponential growth pattern (R 2=0.915, 0.923, 0.849) and the growth of the area and volume followed the quadratic polynomial growth pattern (R 2=0.943, 0.961). The L3 followed the quadratic polynomial rule during 21 to 39 weeks (R 2=0.910, 0.916, 0.914, 0.942, 0.948) The sagittal diameter, transverse diameter and height of the S1 followed the linear growth pattern (R 2=0.905, 0.911, 0.922) and the area and volume followed the quadratic polynomial growth pattern (R 2=0.930, 0.964) during 23 to 39 weeks. Conclusions:The growth and development of C4, T6, L3 and S1 COC of fetus in the second-third trimester has a good correlation with gestational age. The growth of fetal vertebral COC in the early stage is slow, but with the growth of gestational age, the growth rate of vertebral bodies accelerates.