Twins facts, Abuse

[Milz]

I'm getting this out of one of the books here at work.
1. Rate of twining in US is 12 per 1000 pregnancies.
2. Identical twins occur at a rate of 4 per 1000 births (source says 
this is "constant", which I assume to be worldwide).
3. Fraternal twins occur at a rate of 8 per 1000 in the US and 4 to 50 
per 1000 worldwide.
4. 2/3 of all twins are fraternal in the US.

So having two sets of twins at Hogwarts isn't that unusual. However 
having two sets of IDENTICAL twins at Hogwarts can be considered 
unusual, since identical twins aren't as common.

Now for abuse.

I work in a physician's office. Physicians, nurses, teachers, day-care 
workers, etc. are 'mandatory reporters'. If they see anything 
"suspicious", they are mandated by law (in the US at least) to report 
it to the local child services. What defines "suspicious"? Well, it's 
rather subjective and it's a judgement call. 

For example, if a child is brought in for an ear infection and the 
doctor sees a bruise on the child's chest, the doctor must examine the 
child for other marks/signs and must also inquire how the child got 
that bruise. If the story doesn't match the injury, that makes it 
highly suspicious. For example, a 2 month old baby with a sunk-in 
skull fracture and the story is "he was sitting up in his crib and he 
lost his balance and fell and hit the slats on the crib". (2 month old 
babies generally don't have the muscle control to "sit up" and sunk-in 
or depressed skull fractures generally takes more force than a child 
bumping his head).  If the story does match the injury, then it 
becomes less suspicious. For example, a 4 year-old with a scrap on the 
heel of his left hand and a scrap on his left knee with the story he 
was running on the sidewalk, slipped and fell down. In this case, most 
doctors I've worked with don't call child services. 

If a "mandatory reporter" doesn't report "suspicious" marks/injuries, 
then that person can be held liable if something adverse should happen 
to the child. So, calling child services for cat scratches may seem 
ridiculous, but for the 'mandatory reporter' it's a case of CYA (Cover 
Your Ass). To an extent, it's also a way of "spreading the 
responsibility around": you reported it to the authorities, the 
authorites researched it and made a decision. If anything happens to 
the child, you can always say "I did what I was supposed to do."

Milz