Risk factors in Autism?

I had a well-educated family whose kid was diagnozed with autistic spectrum disorder in my clinic yesterday. They were obviously devastated by the diagnosis and had a lot of questions. One of the questions that I felt unable to answer at that point was about whether they should try to have another baby, meaning thereby as to what were the chances of the second baby having the same disease.
Autism is a lifelong neurological syndrome that affects a childs ability to interact with the other people. It is characterized by the abnormal development of communication skills, social skills, and reasoning. Males are affected four times as often as females. Children may appear normal until around the age of 30 months.It limits their ability to interact with others socially, in fact many autism suffers avoid human contact.
Autism Symptoms vary widely in severity, include impairment in social interaction, fixation on inanimate objects, inability to communicate normally, and resistance to changes in daily routine. Characteristic traits include lack of eye contact, repetition of words or phrases, unmotivated tantrums, inability to express needs verbally, and insensitivity to pain.
There is a GENETIC component to autism, however since multiple genes are involved, the actual transmission in quite complex and difficult to predict in a particular family.
However a simplified answer to the question (chances of second baby having the disease) is as follows:

• Overall incidence of Autism 1: 500 ( and possibly increasing!)
• Chances of autism in identical twins 60-90 %
• Chances of autism in fraternal twin 2-4 %
• Chances of autism in a sibling 1: 20 (5%)
• Chacnes of autism in the third child if two kids are autistic 1: 3 (35 %)
• Chances in second degree relatives (aunts , uncles, grandparents, grandchildren) 0.18 %
• Chances in third degree relatives (cousins) 0.12 %

Early intervention is the key to success in treating this condition and limiting the problems faced by these kids.

RED FLAGS (COURTESY : FIRSTSIGNS)

Social/Communication Red Flags:

If your baby shows any of these signs, please ask your pediatrician or family practitioner for an immediate evaluation:

• No big smiles or other warm, joyful expressions by six months or thereafter
• No back-and-forth sharing of sounds, smiles, or other facial expressions by nine months or thereafter
• No babbling by 12 months
• No back-and-forth gestures, such as pointing, showing, reaching, or waving by 12 months
• No words by 16 months
• No two-word meaningful phrases (without imitating or repeating) by 24 months
• Any loss of speech or babbling or social skills at any age