OA (occiput anterior)

OA (osteoarthrosis)

OA (osteoarthritis)

OAE (oto acoustic emissions)

OAG (open-angle glaucoma)

OAVS (oculoauriculovertebral spectrum)

OB (obstetrics)

OB (occult blood)

OB-Gyn (obstetrics and gynecology)

OB/GYN (obstetrics/gynecology)