The following table is an approximation of fetal exposure to radiation from commonly performed imaging studies. This information is adapted from Barraco, Chiu, Clancy, et al from the Eastern Association for the Surgery of Trauma and Wakeford and Little published in Int J Rad Biol 79 (5): 293-299, 2003.
Head CT <0.05 rads Chest CT <0.10 rad Abdominal CT 2.60 rads Plain Radiographs
Chest (2 views) 0.00002 – 0.00007 rads
Cervical spine 0.002
Thoracolumbar spine 0.370