Claim. No reproduction occurs in the spirit world; the earth is the unique manufacturing plant for citizens of the heavenly kingdom, so Blessed Families should not practice birth control.
Elaboration. SMM derives the doctrine from spirit-world topology: “People do not give birth to babies in the spirit world. It is a vertical, circular God-centered world not requiring the birth of babies. As he needed a horizontal base, God created human beings as His embodiment. It is an earthly field of reproduction from which all the citizens of the spirit world originate” (2.8.3. Why we should have lots of children, 205-97, 1990.7.7). The reproductive monopoly of earth is total: “Perfection must be achieved on earth, not in the spirit world… This is why you need to have children. They become heavenly citizens” (ibid, 217-130, 1991.5.12). Hence: “Even if each of you had a hundred children, heaven is so vast that you could never overproduce.” The Blessing-family birth-control prohibition is not pronatalism for its own sake — it is the population mechanism for the heavenly kingdom, which has no other source.
See also. csg-blessing-is-gateway-to-heaven