Factores reguladores de la monocigocia y dicigocia en España (2006)

Abstract

This paper deals with the relationship between the current frequency of monozygotic and dizygotic twins in Spain and some bio-demographic variables such as maternal age, parity, birth interval, rural and urban environment and seasonality of the delivery. Data used in analyses come from a database of the Instituto Nacional de Estadística of Spain in 2006. Results obtained indicate that the monozygotic frequency increase with maternal age, in the short birth intervals (shorter than 24 months), and in rural environments but it decreases from the fifth parity. Regarding dizygotic twins, frequency is higher in first-time mothers, in long birth intervals (longer than three years and a half) and in older mothers. In relation to season variability, the lowest frequency corresponds to the spring.