That, of course, did occur, and part of that was forced breeding by slave owners to continue slavery in America once the slave trade was outlawed. Women forced to give birth to enslave their children.
They are potential humans, but not realized persons with a functioning sense of self or ability to suffer like the pregnant female.
Consider that the female body WILL protect itself against the potential human if it poses a threat:
"Given the invasive nature of pregnancy, it’s perhaps not surprising that the primate womb has evolved to be wary of committing to it. Mammals whose placentae don’t breach the walls of the womb can simply abort or reabsorb unwanted foetuses at any stage of pregnancy. For primates, any such manoeuvre runs the risk of haemorrhage, as the placenta rips away from the mother’s enlarged and paralysed arterial system. And that, in a sentence, is why miscarriages are so dangerous.
It’s also why primates make every effort to test their embryos before they allow them to implant. The embryo is walled out by the tight-packed cells of the endometrium, while an intimate hormonal dialogue takes place. This conversation is, in Haig’s words, a ‘job interview’. Should the embryo fail to convince its mother that it is a perfectly normal, healthy individual, it will be summarily expelled."
Why pregnancy is a biological war between mother and baby | Aeon Essays
The article also describes why some people describe developing fetuses as parasites:
"In primates and mice, it’s a different story. Cells from the invading placenta digest their way through the endometrial surface, puncturing the mother’s arteries, swarming inside and remodelling them to suit the foetus. Outside of pregnancy, these arteries are tiny, twisty things spiralling through depths of the uterine wall. The invading placental cells paralyse the vessels so they cannot contract, then pump them full of growth hormones, widening them tenfold to capture more maternal blood. These foetal cells are so invasive that colonies of them often persist in the mother for the rest of her life, having migrated to her liver, brain and other organs. There’s something they rarely tell you about motherhood: it turns women into genetic chimeras."