From The Official web site of Jehovah's Witnesses:
Nowhere does the Bible command Christians to procreate. God told the first human couple and Noah’s family: “Be fruitful and become many and fill the earth.”
But this command was not repeated to Christians. (Genesis 1:28; 9:1)
Hence, married couples may decide for themselves whether they will raise a family, how many children they will have, and when they will have them.
The Scriptures, likewise, do not condemn birth control.
From a Biblical point of view, then, whether a husband and wife choose to use some nonabortive method of contraception is really a personal decision.
So, there we have it, commands in the Old Testament are meaningless if they are not repeated in the New Testament.
It makes one wonder why they reversed their teaching on vasectomy and say any brother who had one was not eligible to me a MS or Elder? If its the couple decision "and no one should judge them" why do they forbid it?
Isn't it clear that the Governing Body just makes this stuff up as they go along?
Here is a really ridiculous line of reasoning from the Watchtower:
1941 The prophetic picture seems to set forth the correct rule, to wit: The three sons of Noah and their wives were in the ark and were saved from the flood. They did not have any children, however, until after the flood. They began to have children two years after the flood. (Genesis 11:10,11) No children were taken into the ark and none were born in the ark, and hence none were brought out of the ark. Only eight persons went in and eight came out of the ark. (1 Peter 3:20; Genesis 8:18) That would appear to indicate that it would be proper that those who will form the "great multitude" should wait until after Armageddon to bring children into the world. (Children; 1941; 3,000,000 ed.; p. 312-313)
Oh, yeah! That makes sense!