When we say that God is the giver of life, that He blesses us with children through the means of procreation, how are those words being understood? Are we understanding them to mean that God is actually doing the knitting in the womb, or do we understand them to mean that he has put a process in motion that men and women make use of? If it is the latter, then NFP, for instance, may make sense to some.
That's a wise perspective on the topic. Of course God is actually doing the creating. The error we fall into first in almost every sin is thinking that, while God started the ball rolling, we in the world are now in charge (the now "hands off" God having retreated back into His heavenly realm to watch at a distance what his creatures might do with what he has created). This is unfortunately a common worldview among Christians. I've often reminded my opponents in the contraception debate that, as with our spiritual (second) birth, the only thing we can do in procreation is reject God's gift of life. God alone creates life, spiritual and physical. Life is created through the unregenerate as well as the regenerate, and we know the unregenerate are incapable of initiating anything good. In the unregenerate, it is clear that God alone does the good work of procreating through the means of unregenerate man. Yet procreation for the Christian still must be looked at similarly from this perspective:
65] From this, then, it follows that as soon as the Holy Ghost, as has been said, through the Word and holy Sacraments, has begun in us this His work of regeneration and renewal, it is certain that through the power of the Holy Ghost we can and should cooperate, although still in great weakness. But this [that we cooperate] does not occur from our carnal natural powers, but from the new powers and gifts which the Holy Ghost has begun in us in conversion, 66] as St. Paul expressly and earnestly exhorts that as workers together with Him we receive not the grace of God in vain, 2 Cor. 6, 1. But this is to be understood in no other way than that the converted man does good to such an extent and so long as God by His Holy Spirit rules, guides, and leads him, and that as soon as God would withdraw His gracious hand from him, he could not for a moment persevere in obedience to God. But if this were understood thus [if any one would take the expression of St. Paul in this sense], that the converted man cooperates with the Holy Ghost in the manner as when two horses together draw a wagon, this could in no way be conceded without prejudice to the divine truth. (2 Cor. 6, 1: Sunergou'te" parakalou'men: We who are servants or coworkers with God beseech you who are God's husbandry and God's building, 1 Cor. 3, 9, to imitate our example, that the grace of God may not be among you in vain, 1 Cor. 15, 10, but that ye may be the temple of God, living and dwelling in you, 2 Cor. 6, 16.)
[FC, SD, Free Will]
The problem today is belief in the common erroneous sentiment the "God helps those who help themselves." NO! God does it all. He helps us because we CAN'T help ourselves. Everything we do that is of any good is entirely by the power of God, the God who HASN'T retreated to watch from afar, but rather has stayed in intimate relation with us and does not withdraw his gracious hand from all good works that we do - works which were prepared for us to do from the foundations of the world. The shame is that we so often slap his loving hands away with our flailing arms due to our misguided attempts to be in charge ourselves. Nowhere is this more obviously true than in procreation, because no other human activity is so clearly God's business than the creation of souls. As Luther said of the divine ordinance to be fruitful and multiply:
"For this word which God speaks, 'Be fruitful and multiply,' is not a command. It is more than a command, namely, a divine ordinance [werck] which it is not our prerogative to hinder or ignore. Rather, it is just as necessary as the fact that I am a man, and more necessary than sleeping and waking, eating and drinking, and emptying the bowels and bladder. It is a nature and disposition just as innate as the organs involved in it. Therefore, just as God does not command anyone to be a man or a woman but creates them the way they have to be, so he does not command them to multiply but creates them so that they have to multiply. And wherever men try to resist this, it remains irresistible nonetheless and goes its way through fornication, adultery, and secret sins, for this is a matter of nature and not of choice."
[Luther's works, vol. 45, The Christian in Society II, The Estate of Marriage, pp. 15-21]