Autism is a medical condition in which there are problems with communication and social interaction. This is a rather serious condition to be diagnosed without a complex and complete examination. The child might lack eye contact, as you mentioned.
The babbling in these children might be accompanied with unusual gestures, repeating othersâ words, whereas the words are less frequently associated with appropriate gestures. Repetitive behaviour might be one of the symptoms that are most easy to recognize. It might include: compulsive behaviour, ritualistic behaviour, stereotypy, or even self-injury.
As for the slow improvement of the speech, please consider that many children just need more time to talk and to be understood. Different conditions might be causing this situation. Sometimes the child might need help from a specialist for speech and language therapy, whom you are advised to visit.
S/he might be able to detect if there are any physiological problems with the speech-related organs (the tongue, the palate, the throat) or the child simply needs more time to develop the speech.
To exclude autism you might want to take your child to a neuropsychologist pediatrician. Until than, please keep in mind that there are many children at the age of 19 months whose speech is not fluent enough to be understood clearly.