I'm actually going to give a slightly different response as I know someone here who was in a VERY similar situation. Doctor discovered her unborn child was going to have severe birth defects (life threatening and requiring care for the childs entire life). Doctor literally forgot to inform both her and her husband. At her 36 week check-up, one of the midwives examining her mentioned the complication (it was in plain view in her file) and wanted to know if they had located a specialist yet as one would be needed immediately. The couple was horrified as had they known about the complications when the doctor did, they would have potentially made the decision to terminate. Since they didn't know, they are now caring for a severely disabled child. They too are now seeking suit against the doctor for not informing them. Really, this sort of thing happens. Doctors are human and sometimes make mistakes and sometimes those mistakes can have difficult and costly life changing effects.
Remember the Levys' from Portland? They were successful in their suit regarding the misdiagnosis of their Down Syndrome child. Granted, the misdiagnosis came as a result of botched testing, but it was still a successful case in that had they known they were carrying a DS child, they too would have terminated. If OP had been told she was a high risk at the appropriate time, she could have completed the necessary testing to confirm or deny the diagnosis. OP (if this is a real story) was NOT told so she could NOT take the next steps. Now she is beyond the legal limit (in many areas) for termination if in fact her child is indeed DS. If this is a real story, I would take this to an attorney in the area and let them review the facts as this might not be a blanket "You have no case" situation if the details are correct. We're talking about a major life changing decision here, far more than just having the baby in general.