Frecuencias de defectos congénitos al nacimiento en España y su comportamiento temporal y por comunidades autónomas. Causas de las variaciones de las frecuencias

A review is presented of the main aspects arising from the study of the frequency of congenital defects, explaining the importance and use of this knowledge, and illustrating it with different examples based on the analysis of data from the ECEMC (Estudio Colaborativo Español de Malformaciones Congénitas) (Spanish Collaborative Study of Congenital Malformations). From this analysis it was observed that the overall frequency of newborns with congenital defects in Spain has been decreasing gradually for many defects. This drop is mainly a result of voluntary termination of pregnancy (TOP) after the detection of foetal abnormalities. However, other factors, such as the improved care of pregnant women and pregnancy planning, plus the increase in the health culture of the population, could also be having some effect, although a lot less obvious than that due to TOP. This decrease in frequency has not been uniform in all the Autonomous Communities. On the other hand, there are certain defects that have shown a secular increase, arising from the improvement and general use of both prenatal and post-natal diagnostic techniques. Furthermore, it has been observed that the ethnical diversification in our country, resulting from immigration, is also having a certain impact on the frequency of newborns with congenital abnormalities in Spain. These minority population groups, in general, along with the differences in the frequency of certain recessive gene mutations, have socio-health conditions that lead to a higher risk of congenital defects. All these aspects are important and have to be taken into account when designing prevention plans for these diseases.