Does the mother build the baby once it's out of the womb? It still requires nourishment, and historically that would be in the form of breast milk for many months. The baby continues to grow and develop outside the womb and doesn't reach maturity for decades, at what point is it being built by itself and not by something else?

The mother feeds the fetus through the placenta, a parasitic organism, same as she feeds the baby once it's born, same as the child feeds itself into adolescence and adulthood. She doesn't build it.

Except I said at the very beginning, including with my own analogy, that the nutrients come from elsewhere. I never said anything about it being an isolated system, because that would clearly be a) impossible just as a general rule but also b) against the concept of parasitism.. Clearly you have never read anything about parasites because "host" is the other half of the parasitic relationship. If I was a "dumbass Republican" I wouldn't be calling it a fetus, nor would I point out its parasitic nature, now would I? In this context it's purely scientific nomenclature, not political, for me to refer to parasite and host.

And do the hosts build the parasitic organism?

No. They supply the nutrients for the organism to build itself. It's not magic, it's biology.

Talk about bad analogies, Tupperware man, at least the sandwich analogy had a logical throughline.

At least you agree the fetus/placenta is acting parasitically, i.e. it's stealing resources to sustain and build itself, i.e. (here's the big one) not being built by the host.

A fertilized egg isn't just a blueprint. It's a living cell, capable of division as a typical cell tends to be.

The blastocyst builds both the fetus and the placenta, which acts essentially as a parasite, to the point that it secretes chemical compounds and has its own purpose-specific immune cells that allow it to suppress the mother's immune system to avoid being treated as a foreign body. All the instructions come from within the embryo/fetus, all direction comes from within the embryo/fetus. If at any point the embryo/fetus stops providing directions, development stops. The mother doesn't build the fetus, it's just built within her body.

Where does the sperm come from, the mother as well?

The placenta has the same genetic makeup as the fetus. The mother doesn't make it; she supplies the nutrients. It's not a difficult distinction, and yet.. it's still a distinction.

If you buy a loaf of bread at the store, did the bakery make your sandwich? No, it just supplied the materials needed for you to make it.

With the genetic information from the sperm, the fertilized egg utilizes the nutrients available to divide and construct the placenta from part of itself. Without the sperm, the only thing that (unfertilized) egg is doing is flushing out of the uterus.

The placenta is made by the fertilized egg, which is jointly created by the sperm and the unfertilized egg.. so no, the placenta is not made by the mother.

Completely? No sperm, no embryo/fetus/baby and no placenta either.