Another approach to the discussion, besides the pointless argument whether the word "human" includes fetuses or skin cells, is that laws against abortion are inconsistent with the view that people own their bodies, in so far that there is no other circumstance where one person is entitled to the blood, organs, and body of another person.
This is true despite kinship: no laws compels a parent to donate bone marrow, by virtue of being their parent.
And true despite medical need: no laws compel a parent to donate bone marrow, even if their child's life depended on it.
And true despite cause: no law compels a parent to donate their body parts to their child, even if that parents action or inaction (e.g. abuse, accident, genetic disorder) were the reason for their child needing some body part in the first place.
And true despite duration: no law compels a parent to donate a kidney to their child, even on the condition that they will get the kidney back in 9 months or so.
And true despite someone already using your body: if you woke up and discovered another person were hooked up to your body, using you as living dialysis machine, no law compels you to remain hooked together without your permission.
But laws against abortion, which grant unborn children (but not born children) a right to use their mothers blood and organs without her consent, do not make sense in a moral or legal framework where my bodily autonomy takes precedence over whatever life-saving-or-otherwise advantage another may gain by using it.
That's a problem and it needs to be addressed.
Pro-choicers address the problem by conceding that laws against abortion are not consistent with every other accepted norm concerning people using others blood and organs.
Pro-lifers fall back on the view that pregnancy be treated differently, which is special pleading. They might dispute this on the basis that removing a fetus is fatal and infringes on the fetuses bodily integrity; but pro-lifers do not carry that view over to born persons, as there is almost never a circumstance where they argue that mothers ought to be compelled to give up their blood and organs to their born children. We're right back to special pleading again.