The genitals and the pleasure of begetting counteract the distresses of family encumbrances. One would cease to generate altogether if there were not, by the grace of the Lord, a coating, a pleasure-giving substance, on the surface of the generative organs. This substance gives a pleasure so intense that it counteracts fully the distress of family encumbrances. A person is so captivated by this pleasure-giving substance that he is not satisfied by begetting a single child, but increases the number of children, with great risk in regard to maintaining them, simply for this pleasure-giving substance. This pleasure-giving substance is not false, however, because it originates from the transcendental body of the Lord. In other words, the pleasure-giving substance is a reality, but it has taken on an aspect of pervertedness on account of material contamination. In the material world, sex life is the cause of many distresses on account of material contact. Therefore, the sex life in the material world should not be encouraged beyond the necessity. There is a necessity for generating progeny even in the material world, but such generation of children must be carried out with full responsibility for spiritual values. The spiritual values of life can be realized in the human form of material existence, and the human being must adopt family planning with reference to the context of spiritual values, and not otherwise. The degraded form of family restriction by use of contraceptives, etc., is the grossest type of material contamination. Materialists who use these devices want to fully utilize the pleasure potency of the coating on the genitals by artificial means, without knowing the spiritual importance. And without knowledge of spiritual values, the less intelligent man tries to utilize only the material sense pleasure of the genitals.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Second Canto, Chapter 6 – Text 8