The reliability of various tests will also affect a patient’s decision about genetic testing and abortion. The physician should try to give the patient a realistic understanding of what test results mean. No test is without false positives and false negatives. It is never wise to tell a patient that the amniocentesis was normal and therefore the fetus is normal. If the baby is born with a defect that was not detected on the amniocentesis, the family may have more trouble dealing with the problem and may be very angry with the physician who indicated the baby was healthy. On the other hand, a woman who appears to be carrying a defective fetus must understand that many tests are uncertain and there is some possibility that there is no defect. It is difficult to tell a patient this without raising unreasonable hopes. If the decision to abort is made, patients should not be encouraged to ask for testing on the abortus unless this will provide useful medical information for future pregnancies. There is little to be gained from second- guessing an irrevocable decision.