On January 1, 2016, the maternity supplement entered into force in the Spanish pension system. Its impact has been rather scarce. The main objective of this work is to quantify the effect of the application of the mentioned supplement, for which, what happens before and after its implementation is compared. To do this, we first analyze the gender gap in our country. Hereafter, the characteristics of the Maternity Supplement in Spain and in other countries in which a similar complement has been applied are summarized. The analysis of the methodology used is developed in the following section, stopping in the revision of the Internal Rate of Return, the Replacement Rate, the Gender Gap and the Expenditure associated to the complement. In orde...