We’ve all seen the statistics that reportedly the vast majority of Catholic married couples in the Western World practice some form of artificial birth control. The Church teaches that in order to confect a valid sacramental marriage, the couples must be open to life when exchanging their vows. How specific must this opennes to life be? Is it simply a general opennes to having children at some point in the marriage, or would any specific or general plans of using forms of artificial birth control potentially invalidate the marriage? For example - say a couple fully intended to have children - and in fact greatly desired children - but also, either due to poor catechesis or simply a lack of faith, intended to use birth control to space children.
It is still a valid marriage.
If, at the point in time when the couple were married, they truly intended to have children then the marriage is valid. Whatever happens afterwards does not cause the marriage to be invalid.
This sounds like a question for a canon lawyer or whoever might be in charge of examining annulments. I think their goal in such a case, if they were to determine whether a marriage was valid, would be to see if the individuals in question were properly disposed in mind.
Although I'm not a canon lawyer, canon law reads this way:
Canon 1096.1 For matrimonial consent to exist, it is necessary that the contracting parties be at least not ignorant of the fact that marriage is a permanent partnership between a man and a woman, **ordered to the procreation of children through some form of sexual cooperation*.*What that "some form of cooperation" may entail is something probably better answered by a canon lawyer, or in some pastoral way by a priest with specific knowledge of the specific individuals. If one of the parties in the marriage entered the marriage with the conditional mentality that they will enter the marriage on the grounds that they can contracept, I suppose that could be an impediment. But again, I'm not a canon lawyer and do not have authority on this matter.