@captn Brad, there is no way science tells you anything about what to call a fetus/embryo/zygote - whether you use the word child or not, that is political NOT scientific.
Science can say 'we're using this label for phases 1,2 and 3, and label2 for phases 4, and 5...'
And then it goes on to describe using the labels. But it is a requirement of science to define specific language to describe the system first. You can't address a topic without it. It is not the result of sciencing.
Further, science doesn't define personhood, but it does provide the background under which we do so - for social reasons. We care about people because thry are unique, they are complex, and we have choosen to assign value to them.
The uniqueness doesn't come from the DNA, the complexity changes over time. And the choice, well that varies, but some people value humans who look like them more than humans who don't. (This being rascism)
The complexity is the most interesting thing, and it resides almost exclusively in the brain (though there is mounting evidence of the importance of brain-body connections) and a fetus doesn't have the same level of complexity. An adult cow has more complexity - in case i don't say so, i am a pro-choice vegetarian.
Let me be clear, i am not saying you should have less respect for a fetus because it has less complexity than an adult cow. I am saying you lack empathy for adult animals because your morals are twisted and overly human-centered. You lack the ability to care about animals in the same way some humans lack empathy for people of colour.
This appalls me, far more than a woman who choose not to bring a new life into this world.
And while understanding the science of complexity informs my view, it is no a scientific view. It is a social view, a human invention on what I choose to value. You have no claim to being more or less scientific. All humans assign meaning and value to things and doing so is social not scientific.