First of all, Mary-Love is right; ask your priest about this matter. He can address the specifics of the situation much better than any of us can. I will, however, give my opinion. Mary-Love is also right to point out that there are natural methods to temporarily postpone having children for a time for serious reasons only
, including CCLI's STM method. Note that there should be serious reasons for refraining from being open to children in a marriage. These reasons may include questions about health, ability to raise the child AT ALL, and other serious circumstances. "Wanting to spend time together and enjoy the marriage without children" is not such a serious reason. Another method many find helpful is called NaPro, you can find out more information about it here: http://www.naprotechnology.com/
The use of artificial contraception is seriously sinful. It works against the purpose of marriage and contributes to a culture which does not value every life as a good thing, a gift from God. In fact, it contributes to a culture hostile to life by undermining its intrinsic value in the minds of people.
I could find nothing to indicate that the intent to use artificial birth control to postpone
having children does not, in and of itself, render the marriage invalid. I found much to support the position that the intent not to have children at all renders the marriage invalid or is at least grounds for nullity, but nothing about the postponement of children via the serious sin of the use of artificial birth control.
A valid Catholic marriage results from four elements: (1) the spouses are free to marry; (2) they freely exchange their consent; (3) in consenting to marry, they have the intention to marry for life, to be faithful to one another and be open to children; and (4) their consent is given in the presence of two witnesses and before a properly authorized Church minister.
From: http://www.sspx.org/Catholic_FAQs/catho ... mental.htm
However, this does not mean the marriage vows with the condition of limiting children by artificial contraception or natural family planning are invalid. The exclusion of children is certainly a grounds for a declaration of nullity, but only when there is an explicit, provable and positive act of the will to avoid all children, for this is an intention contrary to the substance of marriage itself. The difficulty in such cases is to determine whether it is the obligation of having children which is refused, or whether it is simply the fulfillment of this obligation. (Cf. Bouscaren, Canon Law Digest, I, pp. 532, 533)....This is the case of those selfish couples who are determined to limit the size of their family from the beginning of their marriage. They are truly married, although their marriage is not pleasing to God, and they will never be able to communicate to their children generosity, the spirit of sacrifice, the love of the Cross, of souls and the Church.
From: http://www.scdiocese.org/Ministries/Tri ... fault.aspx
Partial Simulation: Exclusion of Children: If an individual deliberately excludes an essential element or property of marriage, the consent is invalid (Canon 1101.2). The intention against children has two aspects: one is the intention to exclude the conjugal act; the other is the intention to exclude the effect of this act, that is, children. The right to the conjugal act binds at all reasonable times. The use of this right is not required when the duties of responsible parenthood indicate otherwise. The right to the conjugal act has no limitation in time. The right to the conjugal act includes the obligation of not impeding procreation. If one party intended to have intercourse in a natural manner but also intended to always use artificial contraception or to practice abortion, that person would be marrying invalidly. A temporary exclusion of children for legitimate reasons can and often does become permanent as a marriage deteriorates.
However, Canon Law indicates that a marriage is not consummated until artificial birth control is NOT present, presumably because the proper intent of full self-giving is not present in such marital acts.
Can. 1061 §1. A valid marriage between the baptized is called ratum tantum if it has not been consummated; it is called ratum et consummatum if the spouses have performed between themselves in a human fashion a conjugal act which is suitable in itself for the procreation of offspring, to which marriage is ordered by its nature and by which the spouses become one flesh.
An unconsummated marriage is not invalid, but it is dissolvable (by the Pope).
In my opinion, such an intent does not render the marriage invalid. It is, however, seriously sinful and dangerous to the success of the marriage.