There are four types of esophageal atresia (EA):

Type A. The upper and lower segments of the esophagus end in pouches, like dead-end streets that don't connect. Tracheoesophageal fistula (TEF) is not present.

Type B. The lower segment ends in a blind pouch. TEF is present on the upper segment. This type is very rare.

Type C. The upper segment ends in a blind pouch. TEF is present on the lower segment. This is the most common type.

Type D. TEF is present on both upper and lower segments. This is the rarest form of EA/TEF.

The exact cause of EA is still unknown, but it appears to have some genetic components. Up to half of all babies born with EA have one or more other birth defects, such as:
trisomy 13, 18 or 21
other digestive tract problems, such intestinal atresia or imperforate anus
heart problems, such as ventricular septal defect, tetralogy of Fallot or patent ductus arteriosus
kidney and urinary tract problems, such as horseshoe or polycystic kidney, absent kidney or hypospadias
muscular or skeletal problems
tethered spinal cord

EA and TEF are also often found in babies born with VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies and limb abnormalities) syndrome. Not all babies born with VACTERL syndrome have abnormalities in all of these areas.