Concerning the question as to why the Scriptures do not expressly prohibit contraception, the Rev. Matthew Winzer answers:
“First, birth control and contraception are two different things. According to the Bible abstinence is permitted in certain contexts. That amounts to birth control.
Secondly, the use of specific procedures to prevent conception requires the adoption of a philosophy which is contrary to the Bible. As noted, the human body is equated to the life of the lower creation as something which is to be regulated in stewardship. Then sexual relations are reinterpreted as if they possess some unitive benefit apart from being fruitful and multiplying, thus ignoring what the Bible specifically calls “blessing.”
Thirdly, to move the discussion beyond questions of “immorality,” which are only going to muddy the waters, a more positive approach would ask what the Bible sets forth as an ideal. An open view of children as God’s heritage accords with the whole biblical scheme in both its creation and new creation teaching. Temporal family life is always regarded as being enriched by the multitude of offspring. As far as the redeemed family of God is concerned, the statement of our Elder Brother sums up the positive biblical teaching: “Behold I and the children which God hath given me.””
Source: http://www.puritanboard.com/f32/contraception-bible-61208/, Comment #17