Totipotency Reduction

See link for significant background information. We again want a specially crafted virus, similar to what was described there.

A few days after conception, and inside the womb, what was originally a fertilized ovum has become something known as a "blastocyst", which attempts to implant into the womb. Every cell in a blastocyst is a special type of stem cell, a "totipotent" stem cell. So far as we know, this is the only stage of human development where lots of totipotent stem cells exist. Very likely, during the first couple weeks after implantation, all of them will become less-capable "pluripotent" stem cells.

Suppose our specially crafted virus targeted only totipotent stem cells? If sprayed into the womb through the cervix, no part of the woman's body would be affected by that virus. Only the totipotent stem cells in the blastocyst would be affected.

And what do we want this virus to do? Simple! We want them to tell each totipotent stem cell to start processing a different block of DNA code, perhaps muscle-cell DNA code. The entire blastocyst turns into a tiny blob of muscle cells (or other chosen cell-type), and after that, does absolutely nothing. The blob will be flushed out of the womb with the next menstrual cycle, along with any virus particles that did not find a target. (If, the very next month, the woman decides she wants to get pregnant, there will be no virus there, to interfere.)

This is a "morning after" type of birth-control system, but likely needs to be applied for several days, because of uncertainty regarding just when a blastocyst will be THERE, to be vulnerable to this virus.

That's all.