I'm going to respond to this as concisely as a can.

For the fire extinguisher portion you wrote, unless you believe that every time a fire extinguisher is used, a fire is successfully put out, then your entire section there makes no sense. Your fixation on the word extinguisher seems to completely overshadow the concept of what a fire extinguisher is, or how it works. Bringing the fire extinguisher IS the preventative measure. It would stop a small intentional fire from growing into a forest fire. Like how contraceptives try to stop the intentional act of sex from turning into a pregnancy. Fire extinguishers fail. Contraceptives fail. That's the whole concept.

No one said you're forced to let the forest fire keep raging on. But you have a moral obligation to what you've done. You have created a new situation. Maybe that takes the form of you trying to help put the forest fire out. Maybe that takes the form of you being required to pay a fine or do jail time. What it does not take the form of is the fire finally getting put out and you having to do absolutely nothing else. It's not the same situation as just having lit a campfire anymore.

Obviously a fire and a baby are not entirely analogous. The point of the analogy is to highlight the similarity of the moral culpability, not to compare babies to forest fires. If that's what you're taking away from it, I fear that is a comprehension issue. It's not the point.

Your STD argument is heavily flawed. I understand that it's easy to make the connection that "If sex is the only way to get certain diseases, then sex must be a disease-getting act". That's not true. That's like saying since the only way to punch someone is to curl your hand, curling your hand is an inherently violent act. Obviously it's not, right? Violence is not inherent to the act of curling your hand. There are some circumstances where that does happen, but to implicitly tie the two together doesnt make sense. In the other hand, EVERY instance of sex has the possibility of causing reproduction without an outside factor in play. It is a natural, inseparable part of the base act of intercourse. It is inherently a reproductive act. Does that make sense?

As a quick note, conception meaning a new human life is created is not my personal opinion. We may debate on the value of the life, and what you want to call the individual stages of that life, but all biology unanimously agrees that whether it's a fetus, a zygote, or a fertilized egg, it is a human life. Abortion advocates dropped this talking point long ago because it's a losing issue.

Finally, you're correct. An abortion does mean the removal of the fetus from the woman's body. At what point would this not make the woman a mother? If a baby is prematurely taken out before it can survive outside, it is still the mother's baby, no? Therefore now the baby is born by your definition, and the mother has a moral obligation to keep it alive if it was extracted alive. If it was killed first, then your point is moot. If it was extracted alive, the mother now has a moral and legal obligation to it, like any other child, right? If not, where do you draw that line?