Most of my professional career has been spent working in early intervention (ages birth to 3 years). First as a child development specialist for an HIV/drug treatment program in an inner city, then as a program coordinator for an early intervention center based program.
I learned an enormous amount from the staff in each of these settings. And I saw the results that occupational therapy, physical therapy, speech and language therapy could make even when the treatment was minimal (because sometimes that is all some little ones need).
The term early intervention has allowed families to think about therapies in a new way. A way that doesn’t stigmatize, but instead offers a more personalized plan for each child. Most programs also include the family, so services can be seamless between the center or therapist and the home.
This article recounts a mothers reasons for referring her own children to early intervention services.
http://www.weknowstuff.us.com/we-know-stuff/2013/04/the-gift-of-early-intervention.html
Although this is a Canadian based newspaper article (and the funding is a bit different), it also gives a summary of early intervention services and reasons for referrals.
Every city should have an early intervention system in the USA. In California, the referral would be to the Regional Center in your area. Typically, over the age of 3, you would refer to your school system for services.
If you have questions about your little one, start with your pediatrician and early intervention centers to get your questions answered.