Postmarketing analysis of medicines: methodology and value of the spanish case-control study and surveillance system in preventing birth defects.

There are many surveillance systems of congenital defects all over the world; several of them have developed specific approaches to generate and test selected hypotheses regarding human teratogens. However, to the best of our knowledge, none of them have a permanent and systematised programme for the study of the risk and safety of drugs. The aim of this article is to describe the research programme on the potential effects of drugs in pregnancy followed by the Spanish Collaborative Study of Congenital Malformations (ECEMC), which is a permanent ongoing case-control study and surveillance system. The programme to analyse drugs includes a continuous and systematic study on the potential effects of medicines used during pregnancy. This programme has several characteristics that make it different from other current systems: (i) the collection of numerous datapoints (up to 312 per infant) in a case-control design; (ii) the use of a versatile and specific coding of birth defects; (iii) a specific programme for the continuous analysis of the potential effects of each type of drugs used during pregnancy that has been developed specifically for the ECEMC methodology, including its dysmorphological coding system. The description of the ECEMC's approach to surveillance of the effects of drug use during pregnancy may help researches in this area, particularly those using data from birth defects registries.