Baha’i Studies Bulletin Vol I #4 March 1983 pp82
As to the problem of birth control, neither Bahá'u'lláh nor Abdu'l-Bahá has revealed anything direct or explicit regarding this question. But the Bahá'í Teachings, when carefully studied imply that such current conceptions like birth control, if not necessarily wrong and immoral in principle, have nevertheless to be discarded as constituting a real danger to the very foundations of our social life. For Bahá'u'lláh explicitly reveals in His Book of Laws that the very purpose of marriage is the procreation of children who, when grown up, will be able to know God and to recognize and observe His Commandments and Laws as revealed through His Messengers. Marriage is thus, according to the Bahá'í Teachings, primarily a social and moral act. It has a purpose which transcends the immediate personal needs and interests of the parties. Birth control, except in certain exceptional cases, is therefore not permissible.
On behalf of Shoghi Effendi, letter dated 10/14/35 to individual believer,
1935-10-14 to ind re birth control