While the following quote from Martin Luther does not capture everything that could be said about marriage and child-rearing nor reflect adequately on the anguish couples feel when they are unable to conceive children, it is still an encouraging reminder for parents to pursue their calling with purpose, joy, and reverence.
“The best thing in married life, for the sake of which everything ought to be suffered and done is the fact that God gives children and commands us to bring them up to serve Him. To do this is the noblest and most precious work on earth, because nothing may be done which pleases God more than the saving of souls. If the need were to arise, all of us should be ready to die in order to bring a soul to God. So you see how rich in good works the estate of marriage is. God lays souls into the lap of married people, souls begotten from their own body, on which they may practice all Christian works. For when they teach their children the Gospel, parents are certainly their apostles, bishops, and ministers.” What Luther Says: A Practical In-Home Anthology for the Active Christian, E. Plass, 2836.