<i> continuing</i>...
Consider the Fruit. So what was the fruit - the result of widespread acceptance of birth control in America? Within a period of about 40-50 years we had widespread promiscuity, more out of wedlock babies than ever before, rampant marriage infidelity and divorce, and the legalization of abortion with millions of babies being killed. Has it done wonderful things to benefit families? Well, it did result in smaller families for most people. Were the smaller families a good thing? They might seem so in terms of higher living standards and more space per person in homes. But I think you will also find generally weaker families, with less helping and caring for one another. Families in the 1800s weren't perfect, but it seems like there were a lot of large, close and caring families then.
Consider God's Commands. Twice in Genesis God gives the command for us to be fruitful and multiply. There is no record of His ever withdrawing or modifying this instruction. Some will argue that God only meant this to apply for a certain period, until there were lots of people living all around the globe. But without God ever saying "enough", there is no way for us to conclude when it is enough, or if there will ever be enough in God's judgment. Without further revelation, we disobey at our own peril.

But of course this command was given to the human race as a whole. From other Scriptures we know God does not require everyone to marry and that we are not to engage in relations outside of marriage. Also we know that God Himself does not choose to bless everyone with children. So, by God's own choice, not everyone can be fruitful and multiply. But if anything, that just puts the greater requirement of this command on those who do marry and whom God enables to have children. If those of us who are married and able to have children, refuse to be fruitful, multiply and fill the earth, then just who will? As Christians we have the opportunity to further advance the kingdom of God simply by having children and leading as many of them as possible to the Lord. If any people should be having lots of babies, it is Christians.