As Princess Rot, Little Miss and others said, being fertile doesn't mean that a little girl can safely take an adult penis (even if I suspect that Afadly is of the micro-dick variety), much less carry and deliver a baby, and don't even get me started on the consent or mental maturity points.
@Orangutan:
"Wand Sex?"
Thre words: Harry Potter fanfics ^^" Then there is the (true, AFAIK) story about that girl discovering how much fun she could have with the vibrating function of her toy Firebolt broom.
@Tomby Stone:
"Just deal with your problem the way the rest of us do, with a boxset of Lazytown DVDs and a box of Kleenex."
4chan much? ^^"
@tracer:
""In many legal cases in USA they use the term "Treated as an adult", wow they break their own rules"
As repugnant as the whole subject of pedophilia is, this is one sentiment I've gotta agree with.
In California, the legal Age of Consent is 18. If two 17-year-olds have sex together, they are both guilty of Unlawful Sexual Intercourse. The sickening thing, though, is that being so close to age 18, they can be tried as an adult for a crime whose very definition requires them to not yet be adults!"
Yeah, textbook case of the stopped clock still being right twice a day.
The most sickening thing in the situation you describe is that even if they manage to avoid getting prison time, both kids will usually have to register as child molesters, effectively screwing them over for life: absurds restrictions pretty much make it impossible to live anywhere or to finish high-school, finding work becomes equally impossible, and they get continually harrassed (and in some case murdered) by lunatic busybodies and vigilantes who got their name and address courtesy of the government... (not to mention the harrassment suffered by their family, and sometimes by people unfortunate enough to share the name of the "offender" or to live in the house said "offender" previously inhabited).
All that over things that are no crime under any sane definition. I remember reading about a 15yo girl getting convicted of child pornography because she sent a few racy pictures of herself, and other logical disconnects where teens got convicted because they were old enough to fuck, but not old enough to take pictures/home videos of themselves fucking, or old enough to fuck but (due to legal leftovers of sodomy laws) not old enough to get/give a blowjob....
Classically Liberal describes a few specific cases of such child-sex laws perversions.
"Such an enormous social taboo makes it difficult to gather statistics.
I wonder just how many adult men ARE attracted to pre-pubescent girls. While acting on such an attraction would have dire consequences, I'm betting that the number of such men is larger than most of us suppose."
Well, I remember reading an article on Wikipedia that said that during an experiment, an erection-measuring device registered a reaction in about 25 to 33% of the subjects when they were exposed to child porn. That said, this isn't necessarily indicative of genuine arousal, as the jolt of adrenaline associated with violent emotions (such as anger, fear or disgust) can trigger mechanical erection, IIRC.
Unfortunately I couldn't find the article again to check if my memory was correct or to find sources, so take this with a grain of salt. (I think it was the pedophilia article, but it looks like it has been entirely rewritten since I read it).