MSRA-0863

A 35-year-old woman is pregnant with her first child. She is offered screening for chromosomal abnormalities and an ultrasound assessment.
She decides to proceed with testing, which assesses nuchal thickness, pregnancy-associated plasma protein-A (PAPP-A), free beta-human chorionic gonadotrophin (β-hCG) and crown-rump length. She is told the pregnancy is a high risk for Down syndrome, and she and her partner are offered an amniocentesis.
Which one of the following statements regarding amniocentesis is correct?