The rapid global uptake of noninvasive prenatal testing for Down syndrome based on maternal plasma cell-free DNA has provided new data on the interrelationship between cell-free DNA and maternal health. Specific maternal conditions that can affect the performance of noninvasive prenatal testing include obesity, active autoimmune disease and low molecular weight heparin treatment. There is also a growing appreciation of the implications of discordant noninvasive prenatal testing results for maternal health, including unexpected diagnoses of maternal chromosomal conditions, or rarely, occult cancer. The interrelatedness of noninvasive prenatal testing and maternal health mean that the longstanding principles underpinning prenatal screening – voluntary testing, informed decision making, availability of specialist genetic counselling and well-defined clinical pathways – are more important than ever before.