If nothing else, by using contraception, it allows you to fully relax and enjoy the sex. You can lie in each others arms afterward and enjoy the moment without your thoughts running around screaming "ohgodisshepregnantohgodohgod".

However, in this case, the horse has left the stable and all the padlocks in the world won't really help much now. This is going to be amazingly hard in your girlfriend and the fact that she's already been through it once won't make it easier - quite the opposite.

You two need to have a proper Talk - not just about what you decide to do but about your relationship as well. If you two want to make a real go of this, then as Serpy said, you MUST use precautions AT ALL TIMES in future. She already resents the fact that she's had to abort a child twice, something that goes against every bit of "natural programming" in her body. A third time would be a catastrophe. It might also be worth looking into a vasectomy or something of that nature if you adamantly refuse to wear condoms and the like.