FCOG-1152

A 39-year-old woman who is 8 weeks pregnant presented to the medical clinic for consultation regarding the chance of her baby having Down syndrome. She mentioned that she has read somewhere that one of the risk factors for Down syndrome is advanced maternal age. She is concerned and asks if there are ways in which she can know whether her baby will be affected. Which of the following is considered as both the safest and the most accurate diagnostic tool for the exclusion of Down syndrome?