Some thoughts on the subject.
In discussing this subject is there enough clear Biblical material for us to state definitively what God's command is concerning contraception? It would be one thing to argue for what you think God would want for people and suggest things for them to consider when considering contraception. It would be quite something else to start making refusal to use contraception a command from God. It does not seem to me that we have a clear enough command to state such definitively even if we are personally convinced that it is more God pleasing to refrain from the use of contraception than to use it. To state that it is my opinion that Christian couples should not use contraception is different from stating that as a clear command from God.
What about cases where there are medical reasons that it would be better medically for a woman not to conceive?
Clearly, if a birth control method is functioning not as a contraceptive but as an abortificant, that is a different question, subject to all the reasoning and Scripture concerning the taking of life through abortion. But if a method is contra - conception it is not taking a life, but preventing a life from ever beginning. A different question.
How far does one go in the argument that it is illegitimate for a couple to refuse a child if it could have been received. Perhaps one evening the husband is tired, or his wife has a headache - or she has an important meeting the next day and doesn't want her hair mussed up, so they simply sleep together (i.e. in the same bed with no further interaction). That night they could have conceived their next child, or not. They will never know. Have they done wrong by not giving God a chance to give them a baby at that time? Even natural family planning allowed by the Roman church is a contraceptive method, intent on preventing the conception of a child except when decided by the parents. Is that acceptable? Why? What is the big difference between preventing conception by refraining from intercourse at certain times, and doing so by using other methods? Or are we to take the refraining from sex as the "punishment" for not having more children?
I can well understand people deciding that God's will for them is to not use contraception, and arguing that they think it is more God pleasing. I would be less open to making it a church teaching that all "artificial" methods of birth control are contrary to God's will. (Even natural family planning relies in part on artificial equipment, special thermometers, recording keeping and a good medical knowledge of women's cycles - other wise the old joke becomes even more likely - what do you call a woman who uses natural family planning? Mom.)
The decision to not have children, or not have more children, or to not have children right now is an important one that should be carefully considered. One consideration should be the motives of the couple. If it is out of selfishness that needs to be considered and repented.
Dan