What ever it is, it has no individual rights until viability (IMO). Until then, it's the mother's rights that are primary. As you point out about "goo", I think it's important to point out this:
Why can't a fetus be claimed as a dependent?
Why doesn't an embryo have an SS number or benefits?
Why do people say I have 3 children and one on the way instead of 4 children?
If you had an embryo and a baby already born and could only save one...which would it be?
Why is it far fewer seem to care about the hundreds or thousands of leftover embryos in storage that are eventually discarded or given to research? Where's all the fuss about genocide?
It isn't so black and white and the problem, from my view, is heavily one of rights (I don't believe in any inherent sanctity of human life above all other life) but I do believe in the right to make decisions on my own body and medical care, and as long as what is in my body, blastocyst, embryo, fetus, child, baby - all are accurate - can not exist outside it, it is part of my body and not an independent being with rights.
Why can't a fetus be claimed as a dependent?
Why doesn't an embryo have an SS number or benefits?
Why do people say I have 3 children and one on the way instead of 4 children?
Why do most women, shortly after pregnancy, but before the baby is born, form a strong emotional attachment? If it was just goo, it would be silly to form an emotional bond with it.