The celebration of marriage between two Catholic faithful normally takes place during Holy Mass because of the connection of all the sacraments with the Pascal mystery of Christ. 
It is therefore fitting that the spouses should seal their consent to give themselves to each other through the offering of their own lives by uniting it to the offering of Christ for his Church made present in the Eucharistic sacrifice, and by receiving the Eucharist so that , communicating in the same Body and the same Blood of Christ, they may form but “one body” in Christ.  

[1621, Catechism of the Catholic Church]