When the Bible was written, the only way to prevent pregnancy was to abstain from sexual relations. Today we have all kinds of methods which allow people to have sex without having to 'worry' about a pregnancy occurring. So it is difficult to construct a biblical doctrine on this topic. Here is what we can say: 1) that from the beginning, one of the key reasons for the marital relationship has been procreation: that the Bible gives us many examples of women who were greatly distressed because they had not given birth (e.g. Sarah, Rachel, Hannah); and 3) that the Bible seems to endorse the idea of having lots of children. For example, Psalms 127:3-5 says, 'Behold, children are a heritage from the Lord, the fruit of the womb is a reward. Like arrows in the hand of a warrior, so are the children of one's youth. Happy is the man who has his quiver full of them.'
I think that taken together, we can say that God would like His people to forgo the modern methods of contraception and have as many children as He would choose to give them. It has only been since the 1960s that people had any other viable option.