It kinda puts the lie to "With great power, comes great responsibility.", don't ya think?
Perhaps you need to go back to the scene when this all happened in the first place? Maybe it should all go under the heading of unplanned sex, sub-heading, unplanned sex when you are not thinking straight, i.e. wounded, almost killed, drunken by vamp venom, sub-sub-heading of having unplanned sex with someone you truly love who you haven't seen in ages who could kill you during the sex act.... The thought of birth control apparently was way down the list for
both parties... I don't recall Susan asking or insisting on Harry wearing a condom, nor Harry replying with the line that his pleasure is better if he doesn't wear anything, nor her refusing sex if he didn't.. Nor him asking her if she was on the pill or wearing any device for birth control, nor refusing to do anything if she wasn't.. Looks to me like the irresponsibility was mutual..