VACTERL association: A nonrandom association of birth defects. VACTERL is an mnemonic in which the letters V, A, C, T, E, R, and L each stand for one or more type of malformation:

• V = Vertebral anomalies; and
• A = Anal atresia (no hole at the bottom end of the intestine);
• C = Cardiac defect, most often ventricular septal defect;
• TE = TracheoEsophageal fistula (communication between the esophagus and trachea) with esophageal atresia (part of the esophagus is not hollow);
• R = Renal (kidney) abnormalities; and
• L = Limb abnormalities, most often radial dysplasia (abnormal formation of the thumb or the radius bone in the forearm).

The VACTERL association has been recurrently observed in newborn babies. It is more common in the children of diabetic mothers than in the general population. For some years that was all that was known about the cause of the VACTERL association.

The VACTERL association was linked in 2001 to inhibition of cholesterol synthesis and down-regulation (the damping down) of what is called the cholesterol-dependent sonic hedgehog morphogenetic pathway. (This is a biochemical pathway in the shaping of the embryo that requires cholesterol.)

Case reports have suggested that the VACTERL association may possibly occur with increased frequency in children whose mothers have taken the cholesterol-lowering statin drugs in the first trimester of pregnancy. (These drugs are contraindicated in pregnancy.)

VACTERL: A nonrandom association was reported of vertebral defects, imperforate anus, and tracheoesophageal (TE) fistula was first reported in 1968. Over the years, the spectrum of malformations in the association was recognized to be broader. It became the VATER association (or VATERS association) and, now, has been extended as the VACTERL association.

Association: In dysmorphology (the study of birth defects), the term "association" refers to the nonrandom occurrence in two or more individuals of a pattern of multiple anomalies (birth defects) not known to be a malformation syndrome (such as Down syndrome), a malformation sequence (of events) or a polytopic field defect (in which all of the defects are concentrated in one particular area of the body).