There are several things involed.
We also belive in batisim by desire (i.e. the theif on the cross) So by their desire to join in union with the Lord the Catechumen pleases the Lord.
Those in danger of death should always be addressed in a more ugent mode.
The tradiation of the Church is to confir all three sacrements to adults as close to each other as possible. Thus the greater need for education and understanding.
We babtise babies with the promise of the parents and god parents to provide that education after the fact.
I sure othere can provide more infomation to this then I can
The following is some of the church law govering baptisim just for refernce and intrest

[qoute]
Can. 865 §1 To be admitted to baptism, an adult must have manifested the intention to receive baptism, must be adequately instructed in the truths of the faith and in the duties of a Christian, and tested in the Christian life over the course of the catechumenate. The person must moreover be urged to have sorrow for personal sins.
§2 An adult in danger of death may be baptized if, with some knowledge of the principal truths of the faith, he or she has in some manner manifested the intention to receive baptism and promises to observe the requirements of the Christian religion.
Can. 866 Unless there is a grave reason to the contrary, immediately after receiving baptism an adult is to be confirmed, to participate in the celebration of the Eucharist and to receive holy communion. [/qoute]