It will then need at least 5 but generally 9 months of full life support before it has any chance to survive as a separate individual.
A newborn child still has no chance to survive as a separate individual . You've attempted to distinguish a child in the womb as unable to survive independently and a newborn child as able to survive independently. This is patently untrue.
I assume your reasoning is that this affords those willing to extinguish the life of an unborn child the mentality that it is just a 'parasite' - an attempt to cloud judgement on the core issue.
...does a woman have an obligation to make sure each ovum is fertilized? It is, after all a human cell that will naturally develop if only that minimal support is given to it.
No, that makes no sense. An ovum is one part of the puzzle needed before a life can grow. An ovum by itself will never turn into a growing human. Not difficult to conceptualize, it's not a growing human before fertilization.
And therein lies the point. Once fertilized, there is no denying that the "collection of cells" (which I reiterate, we all are) will become an adult human.
Forgive me if I misinterpret you, but it sounds like you do believe you should impose this upon others (take a stand).
You're use of the word impose seems like an attempt to sully my position on this - especially given your past arguments, but yes - just like we 'force' people against their will to murder others in the street, I believe we should do the same for the innocent, defenceless, unborn child.
Turn the tables a bit. Given your thoughts on the subject, it seems that you would believe that it is fine to kill unborn children?
Where there's a will, there's a relative.