Secular decreasing trend of the frequency of hypospadias among newborn male infants in Spain

BACKGROUND: The frequency of hypospadias is not uniform worldwide. Several countries have reported an increase in its frequency at birth. Although a better ascertainment of the minor forms has been considered as an explanation, the potential effect of environmental endocrine disrupters has also been proposed. We studied the secular trend of hypospadias in Spain over the past 22 years, separating the minor and major forms. METHODS: We used data from the Spanish Collaborative Study of Congenital Malformations (ECEMC) registry, analyzing the frequency in two different periods: from 1978 to 1995, and from 1996 to 2002. To evaluate the step of the frequency between the two periods, we applied a parametric Student's t-test, and the nonparametric Mann-Whitney rank test. RESULTS: The birth frequency of isolated and total hypospadias was quite stable between 1978 and 1995. In 1996, it decreased dramatically in a step, essentially due to isolated cases with minor forms of hypospadias. Study of the geographical distribution by the 17 Spanish regions showed that the frequency step occurred in nearly all of them. CONCLUSIONS: It is difficult to consider that the observed decrease of the frequency of minor forms of hypospadias could be due to less accurate reporting of these minor forms in all 87 hospitals in the same year without any previous physician agreement. This decrease rather suggests a change in some product or exposure affecting the whole country. We think that the observed change in the frequency cannot be attributable to a lower exposure to endocrine disrupters or the voluntary interruption of gestation.