ALT Image about microtia. Text includes information about microtia, including: Microtia, is a congenital anomaly affecting the outer ear where the ear does not fully develop during the first trimester of pregnancy. A Microtia ear is often smaller in size, can have a different shape, or be completely absent at birth. Microtia is often accompanied by Atresia. Atresia is the absence or closure of the external auditory ear canal. Microtia occurs in every 1 out of 6,000 to 12,000 birth. There is also an image of a young boy. The boy is wearing glasses and a hearing aid which is connected to the side of the head. He one ear showing in the image and the has microtia.] He is wearing a blue checkered shirt and a blue jumper.