The use of MRI as an adjunct measurement to ultrasound in multiple fetal anomalies has shown beneficial effects, particularly in central nervous disorders. MRI may be valuable for differentiating the etiological heterogeneity that leads to arthrogryposis and fetal akinesia-hypokinesia deformation sequences and identifying related central nervous system abnormalities. Prolonged restriction of fetal movement in the third trimester has a favorable prognosis with the appropriate orthopedic intervention. Conversely, most fetal motor disorders due to congenital neuropathy result in an adverse pregnancy outcome due to hypoplastic lung
[47][30]. Some neurological diseases, such as fetal akinesia deformation sequences, do not respond well to prenatal DNA diagnosis; therefore, prenatal imaging diagnosis plays a vital role in discovering and detecting these diseases
[48][76]. With the improvement in the level of detection accuracy, cine-MRI began to be used to detect the whole fetal movement
[33][69]. On this basis, the examination of fetal lower limbs is becoming increasingly accurate. Developmental hip dysplasia can be analyzed and calculated by cine-MR image sequences to capture the motion at the hip joint
[49][31]. Dysplasia of the hip is the most common abnormal joint shape disease, especially when fetal breech presentation happens with fetal abnormal movement, which then affects prenatal musculoskeletal development and joint shape development
[36][35]. Studies have used adult models and the 2D FE method to calculate fetal lower limb kicking force, and lower limb muscle exertions, stresses and strains
[32][36][50][33,35,77]. The average uterus displacements for kicking in utero were calculated using a custom tracking software and the finite element method, then using the musculoskeletal model to predict fetal kicking of the hip joint and knee surrounding maximum muscle forces
[32][33]. By observing the uterine wall deformation and fetal skeleton development, it was found that stress and strain stimulation increases over the second half of pregnancy
[50][51][77,78]. Altered biomechanical stimulus by stress and strain in the hip joint and kick forces may reveal the link between the risk of developmental dysplasia of the hip and the specific endouterine environment
[36][35]. A series of measurement methods can effectively improve the measurement of fetal lower limb movement.