Resultados de Vigilancia Epidemiológica de los defectos congénitos sobre los datos del ECEMCAs a part of the usual surveillance of congenital anomalies performed in the ECEMC (Spanish Collaborative Study of Congenital Anomalies) database, we have analysed the information gathered in the period 1980-2003, during which a total of 1,941,742 newborn infants were surveyed. The ECEMC registry covered 26.48% of total births occurred in Spain in 2002. We have studied the global prevalence of infants with congenital anomalies in 3 different periods: a) before the passing of the law permitting voluntary interruption of gestation -VIG- following prenatal detection of anomalies (1980-85); b) after such passing (1986-2002); and c) year 2003. The baseline frequency of congenital anomalies corresponds to the period 1980-1985. Comparisons with this baseline mainly indicate the impact of VIG on the birth prevalence for defects which are prenatally detectable. The global prevalence continues diminishing over the years, and the significant decrease can also be observed in 13 out of 17 Spanish Autonomic Regions. All these decreases are mostly attributable to the impact of VIG. When studying the time distribution of the frequency of some selected anomalies, as well as their geographical distribution, we have observed that VIG plays an important role. However, it is difficult to get information on VIGs. The problem is that if it is not registered on a routine basis and with complete data on exposures and other variables, it will be impossible to perform analytic studies on the causes of birth defects . A question that has recently raised is the increasing number of immigrants in Spain. We have analysed the distribution of the control group of the ECEMC by country from which the parents come from. On the other hand, we have also analysed the evolution along the time of the proportion of different ethnic groups in the control group. Finally, in spite of the decreasing frequency of congenital anomalies, it should be considered that such decrease is mainly due to the impact of VIG, so we underline the need of investigating in order to reach primary prevention of birth defects, and applying the known preventive measures, getting infants being born healthy.N
