Your argument is invalid – it completely “begs the question.” You’re putting your conclusion in as a premise (the “Law of Consent”):

All conceptions occur via sexual intercourse
All conceptions may naturally abort
Some conceptions naturally abort
(Consent to sexual intercourse is implied consent for abortion)
——
Therefore: All conceptions have implied consent for abortion

Even with a possibility of natural abortion through miscarriage, how does that make elective abortion morally acceptable? Are you saying any externally induced abortion is natural? Are you arguing moral choices are natural acts? That makes about as much sense as saying murder is not wrong, because someone was going to die anyway, and another’s choice to kill is merely part of a natural process of death.

You misattribute a non-universal (some risk there may be a natural abortion) as a universal basis for elective abortion. That is, acceptance of some risk is actually acceptance of all risk – including the mother making a choice.

You’d probably find the following situation morally wrong: A woman and a man agree to have a child together. After intercourse a child is conceived. The woman then decides she doesn’t want to be pregnant and so aborts the child, against the consent of the man. Is her responsibility towards fulfilling the initial agreement no longer valid because she’s made a different choice later? Should the man bear all risk in the agreement – including her reneging on the initial agreement? Does she bear no liability at all? How is that just for the man?

Here’s an analogous scenario – a man agrees to protect a woman. Later he decides he doesn’t want to protect her, so he kills her. Is his responsibility towards fulfilling the initial agreement no longer valid because he’s made a different choice later?

If you don’t find those situations morally wrong, then apparently you have absolutely no understanding of positive law. You’re conflating natural law and positive law.

You’re not making a valid argument – but simply attempting to dress a bad argument up in “scientific” clothes.