As far as I know, no studies have been done that would allow such a determination to be made with any reasonable degree of certainty. (Until quite recently, most doctors and scientists did not even acknowledge the existence of autistic adults who got married and became parents.) And genetic testing, at this point in time, is very crude and inaccurate.
Of course, like most questions, this one is much more complex than its literal or surface meaning. I have to wonder: What does it say about our culture that this question is even being asked? My personal perspective on this issue comes from being part of a family where autistic traits are so common that they're seen as just part of ordinary life. In my extended family, some kids are early readers, some wander off if they're not watched closely, some enjoy sports, some are nature lovers, some arrange their toys in precise patterns and don't let anyone touch them, and so forth. We don't sort our family members into different categories based on these characteristics; it's just part of who they are.
As a result, I've never drawn the sharp distinction between autistics and non-autistics that many people do. I've known many autistic folks in real life, and to me, they just seem like ordinary human beings, not all that much different from anyone else.
To make myself clear, I'm not arguing that the autism label has no value or that it should be junked. It's useful to the extent that, in describing a general pattern of cognitive and behavioral characteristics, it enables people who have such characteristics (or whose children do) to gain access to potentially helpful information about educational methods, daily life strategies, and so forth. However, when we identify children as autistic, we should keep in mind that there is just as much natural developmental variation among autistic children as there is among any other group of human beings. They don't all have identical traits, and they don't all have identical needs. The label should be just a starting point to provide some guidance in discovering their individual strengths and weaknesses.
I'm aware that there are many people who would never consider eugenic abortion but, nevertheless, would want genetic counseling and/or prenatal testing so as to know in advance their child's chances of being autistic. That's quite understandable, given how poorly adapted our society is to the needs of the autistic minority population, and I wouldn't fault anyone for having that point of view.
Still, there are other questions that prospective parents might want to ask, such as these: What are my child's chances of being able to attend a school where he or she will be able to flourish, regardless of neurotype? What are my child's chances of being able to pursue a career that is well suited to his or her individual talents and interests, without discrimination of any kind? What are my child's chances of being able to obtain appropriate accommodations for his or her differences or disabilities, in the event that such accommodations become necessary for any reason? And what can I do, right now, to change society in such a way as to improve those chances?