Can amniocentesis results be wrong?

Accuracy depends on the condition being tested, the laboratory method and whether the sample contains enough suitable fetal cells. A result only answers the genetic or clinical questions included in the requested analysis; it is not a complete assessment of every possible condition.

Sometimes cells do not grow adequately, the sample is mixed with maternal cells, or the laboratory finds mosaicism, meaning the tested cells do not all show the same genetic pattern. A technical limitation or a finding of uncertain significance can also prevent a simple positive or negative answer.

Discordance may also arise when an earlier screening result and amniocentesis appear different. Screening such as NIPT estimates chance using placental material in maternal blood, whereas amniocentesis examines cells in amniotic fluid. The tests therefore measure different material and serve different purposes.

Ask the fetal medicine or genetics team to name the exact finding, whether the report is definitive, and which limitation is recorded by the laboratory. They may review the ultrasound, compare parental samples, request another laboratory method or discuss repeat sampling when the answer could change pregnancy care.

Do not make major decisions from a screening report, an informal summary or a single term you do not understand. Request the written result and an explanation of what it means for the pregnancy, what remains unknown and how soon clarification is possible.

A confusing laboratory result is not itself an emergency. After the procedure, however, contact the maternity unit promptly for vaginal bleeding, fluid leakage, fever, chills, contractions or abdominal pain that persists or worsens. Go to emergency care for severe pain, heavy bleeding, fainting, breathing difficulty or sudden deterioration.

Ask which cells and genes or chromosomes were examined, whether maternal cell contamination was excluded, and whether mosaicism is suspected. Clarify whether another test could resolve the uncertainty and how either possible answer would affect monitoring, birth planning or newborn care.