I don't think there are tell tale signs of Autism in infants/babies.
I found this at this website:
http://www.autism-pdd.net/autism-symptoms.
html
Autism, which affects thought, perception and attention, is not just one disorder with a well defined set of symptoms; autism is a broad spectrum of disorders that ranges from mild to severe. In addition, the behavior usually occurs across many different situations and is consistently inappropriate for their age.
In the diagnostic manual used to classify disabilities, the DSM-IV (American Psychiatric Association, 1994), “autistic disorder” is listed as a category under the heading of “Pervasive Developmental Disorders.” A diagnosis of autistic disorder is made when an individual displays 6 or more of 12 symptoms listed across three major areas: social interaction, communication, and behavior. When children display similar behaviors but do not meet the criteria for autistic disorder, they may receive a diagnosis of Pervasive Developmental Disorder-NOS (PDD not otherwise specified).
Problems in social relatedness and communication.
(Difficulty in mixing with other children; prefers to be alone; aloof manner; difficulty in expressing needs; uses gestures or pointing instead of words ).
Abnormal responses to one or a
combination of senses; such as sight, hearing, touch, balance, smell, taste, reaction to pain.
Sustained odd play.
Uneven gross/ fine motor skills.
Not responsive to verbal cues
acts as deaf.
Little or no eye contact.
Insistence on sameness; resist changes in routine.
Noticeable physical over activity or extreme under activity.
Tantrums; displays extreme distress for no apparent reason.
Autism Resources
Speech and language absence or delays. Inappropriate laughing and giggling. Echolalia (repeating words or phrases in place of normal language).
Abnormal ways of relating to people,
objects and events. (Inappropriate
attachment to objects; don't seek cuddling )
Spins objects.
An aspect of language that tends to be disturbed in autistic people has to do with knowing how to use language appropriately and in context. That includes knowing how to hold a conversation, thinking about what the other person in a conversation understands and believes, and tuning in to the meta - linguistic signals of the other person, such as facial expression, tone of voice and body language. It is important to remember that communication is as much nonverbal as it is verbal, and autistic people have great difficulty understanding nonverbal language.
The following is from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM IV):
DIAGNOSTIC CRITERIA FOR 299.00 AUTISTIC DISORDER
A. A total of six (or more) items from (1), (2), and (3), with at
least two from (1), and one each from (2) and (3)
(1) qualitative impairment in social interaction, as manifested by at least two of the following:
a) marked impairments in the use of multiple nonverbal behaviors such as eye-to-eye gaze, facial expression, body posture, and gestures to regulate social interaction
b) failure to develop peer relationships appropriate to
developmental level
c) a lack of spontaneous seeking to share enjoyment, interests, or achievements with other people, (e.g., by a lack of showing,
bringing, or pointing out objects of interest to other people)
d) lack of social or emotional reciprocity ( note: in the
description, it gives the following as examples: not actively
participating in simple social play or games, preferring solitary
activities, or involving others in activities only as tools or
"mechanical" aids )
(2) qualitative impairments in communication as manifested by at least one of the following:
a) delay in, or total lack of, the development of spoken language
(not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)
b) in individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
c) stereotyped and repetitive use of language or idiosyncratic
language
d) lack of varied, spontaneous make-believe play or social
imitative play appropriate to developmental level
(3) restricted repetitive and stereotyped patterns of behavior,
interests and activities, as manifested by at least two of the
following:
a) encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in
intensity or focus
b) apparently inflexible adherence to specific, nonfunctional
routines or rituals
c) stereotyped and repetitive motor mannerisms (e.g hand or finger flapping or twisting, or complex whole body movements)
d) persistent preoccupation with parts of objects
B. Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years:
(1) social interaction
(2) language as used in social communication
(3) symbolic or imaginative play
C. The disturbance is not better accounted for by Rett's Disorder or Childhood Disintegrative Disorder
Diagnostic Criteria For 299.80 Asperger's Disorder
Diagnosing and Evaluating Autism
Autism and related disabilities, such as PDD-NOS (Pervasive Developmental Disorder - Not Otherwise Specified), and Asperger's Syndrome are difficult to diagnose, especially in young children where speech and reasoning skills are still developing.
It is essential that the process of diagnosing Autism & related disabilities include the assessment and evaluation of a child's development, communication, and social skills.
Evaluation and assessment are ongoing processes. Once a diagnosis has been reached, this process should be repeated periodically.
We included brief descriptions of some medical tests and evaluations that may be ordered for children suspected of having autism or a related disability.