It is easier for parents to make decisions regarding their child's sexuality if they proceed thoughtfully and cautiously. Sexuality is always a matter of informed consent between two adults. Factoring in the mental age of your child and her social abilities is essential. Unfortunately, no policy can exclude the possibility of sexual conduct that is unplanned, and for girls on the autism spectrum, this is a problem.
Most states do not allow permanent methods of birth control to be used on children, even if they are over the age of majority. There are no exceptions to those laws for children with disabilities. If your child is impaired enough that having children is out of the question, check with a gynecologist and the laws in your state to find out what can and cannot be done.
So how do parents prevent an unplanned pregnancy that is the result of their child engaging in sexual contact without understanding the implications of the activity? Many physicians will prescribe a birth control method for girls with autism or other spectrum disorders that can be taken daily in a pill form, injected every few weeks (frequency depending on the patient), or implanted. The advantage to the injections or implants is that the concern is removed without the daily use of a pill. The disadvantage can be the possible side effects of these methods of birth control, including weight gain, headaches, and problems that may be associated with long-term use of these medications.
It may be unfair that parents of boys with autism do not have as much to be concerned about in this area, but the reality is that girls are at a much higher risk for the consequences of sexual activity. It is not necessary to make a point at this time regarding the responsibility of sexual behavior; the important issue is to protect your daughter.