Here is a hypothetical example of what may be a very common situation.

Bill and Martha have been seeing each other for four years. Both were raised in Catholic families, but were not baptized. They are not married, but instead, they had been living together for a while now. Now Bill sees that both want to continue in their relationship, and because of their upbringing, they would like to get married under the Catholic Church.

Would it make any difference if Bill and Martha got married before they were both baptised, or after?