Fetal karyotype: can we always trust its result?

We retrospectively investigated six cases of discrepancy between prenatal fetal karyotype and postnatal findings. In five cases, the chromosomal abnormalities initially found by CVS or amniocentesis were not confirmed by later analyses and postnatal examination. In one case, the fetal karyotype found to be normal by CVS had to be checked due to sonographic features and clinical anomalies found after birth. In most cases, the normal development on sonographic examination raised the doubt about the abnormal fetal karyotype. Discrepant findings between fetal karyotype results and sonographic findings require great caution in their interpretation and counseling of parents. Placental confined mosaicism seems to be the most frequent cause of such discrepant results. The interpretation of fetal karyotype results should always be correlated with sonographic and clinical findings.