As a gynaecologist we don't deal with Autism so frequently and I counselled her as per my MBBS level knowledge of the condition which was mostly correct but that made me read more about it,just in case there are other such parents who might be having similar questions.
Autism is usually diagnosed by altered behaviour,communication and socialization developing before 36 months of age.
The reason for Autism isn't very clear yet and it can be multi factorial like exposure to chemicals (teratogens),Intra uterine or extrauterine Infections like Cytomegalovirus,Rubella and Toxoplasma and of course complex involvement of genes have also been associated.
Till date scientists have not been able to pick any specific genes and thus intrauterine detection of autism is thus not possible at this point of time.It has been stated that those who have an affected child the chances of second child also having the condition increases.If there are multiple members of the same family with such disorder the risk certainly increases many fold.
At the moment I have referred her to the Foetal medicine specialist.If the Foetalmedicine experts adds anything new I shall be updating this post.