U.S. Air Force Airman 1st Class Chelsea Walker, an aerospace medical service technician assigned to the 633rd Medical Group, applies a sterile probe cover prior to a pelvic ultrasound probe at Langley Air Force Base, Va., Nov. 23, 2015. A pelvic ultrasound allows doctors to examine female reproductive organs and fetuses during gestation. (U.S. Air Force photo by Senior Airman Aubrey White)