This is a tough sell with some doctors, who may not be comfortable due to issues of informed consent. You will need to find a doctor who is educated in dealing with menstruation issues in developmentally delayed women. There are many options available today to lessen the frequency of periods, some of which may lead to less frequent periods than seasonale actually. The most important factor is finding a doctor who is experienced in this field, who can take your daughter's entire health into consideration, and give you the best possible advice for her--does your local children's hospital have a physician's referral service? Perhaps a pediatric/adolescent gynecologist would be the best bet.
A google search of the terms "menstruation developmental delay" should lead you to more information.
Isn't 9 a bit young to start your cycle? I guess I was on the very late side at age 14. How safe is it for a preteen to be on birth control? I mean, that stuff messes with your hormones and teens already have messed up hormones. Would it increase her risks for breast cancer or other cancers later in life? I guess the big thing is finding out if there is any reason not to do it, and if there are no good reasons the doctor can say not to, go right ahead. I would have loved to have my period once every 3 months as a teenager. Actually, I would as an adult. But I'm too chicken to try something. Actually if I'm too chicken to try something like that... well, anyways, if the girl wants to try it out, it should be partially her choice too.
You really need to find a doctor who has experience of these issues with children with special needs.
There are also times when medication to reduce sex drive can be very useful. But again, you need a doctor with experience and you also need to know all the pros and cons of any medication prescribed for your daughter.
Drs. Mark and David Geier seem to think there is a relation with mercury and testosterone levels.
The Geiers noted that people with autism had lower levels of glutathione (unsure of spelling). They found that testosterone blocks the body’s ability to make glutathione. And that mercury binds itself to glutathione. So. whatever the body makes, testosterone takes away. I think they found that testosteone binds itself with mercury as a result.
A well known effect of high testosterone is early puberty. The Geiers went looking for signs of precocious puberty in the autistic children in their clinic and found about an 80% incicence in their patients.
Lupron is a drug known for lowering testoserone levels. It has been to control precocious puberty.
The Geiers theorized that if they were able to temporarily turn off testosterone production with lupron, they might be able to release these trapped stores of mercury.
As with any rersearch, the findings need to be peer reviewed and patients observed long-term and against a control group. The Geiers claim to have treated 200 patients with good results.
I'm not saying that this is the silver bullet, but they may be onto something.