Thalidomide, mainly used for the treatment of leprosy, is a current teratogen in 
South America, and it is reasonable to assume that at present this situation is 
affecting many births in underdeveloped countries. Moreover, the potential 
re-marketing of thalidomide for the treatment of a large variety of diseases may 
extend the problem to the developed world. When the drug is available, the 
control of its intake during early pregnancy is very difficult since most 
pregnancies are unintended. The ongoing occurrence of thalidomide embryopathy 
cases went undetected by the ECLAMC, due to several factors: (1) low 
populational coverage through this monitoring system; (2) pre-existence of the 
teratogen with its effects present in both baseline (expected) and monitored 
(observed) materials; and (3) lack of a defined phenotype to be monitored. Thus, 
if thalidomide re-enters the market throughout the world, due to the wide range 
of new applications, occurrence of phocomelia alone might not be sufficient to 
detect its effects. By a case-reference approach, the ECLAMC registered 34 
thalidomide embryopathy cases born in South America after 1965 whose birthplaces 
correspond to endemic areas for leprosy. Phocomelia was found in five of eleven 
fully described cases. Thus, phocomelia alone is neither specific nor sufficient 
to serve as a suitable phenotype to survey the teratogenic effects of 
thalidomide. Therefore, a thalidomide-like phenotype, defined as any bilateral 
upper and/or lower limb reduction defect of the preaxial and/or phocomelia 
types, should be included in the routine surveillance of birth defects in all 
programmes.