Sonogenetics in fetal neurology.

Fetal imaging technology has been advancing remarkably and prenatal detection and diagnoses have been moved forward from the second and third trimesters to the first trimester. Structural abnormalities detected by fetal imaging often lead to prenatal diagnoses of genetic disorders. However, there are still dilemmas in fetal diagnoses in normal karyotype cases with strong suspicion of congenital genetic disorders from sonographic findings. When fetal sonography reveals multiple minor abnormalities originating from various organs, counseling dilemmas and parental anxieties become greater than before karyotyping. Array-comparative genomic hybridization (aCGH) was developed as a high-resolution analysis of DNA copy number variations (CNVs). In seven cases presenting with abnormal brain structures by fetal imaging, abnormal CNVs were confirmed by aCGH but conventional karyotyping yielded normal results. Although careful patient selection is required in order to deal with microarray results and parental counseling, 'sonogenetics' - incorporating the idea of 'fetuses first' - will play an important role in the era of molecular genetics. Recent advances in non-invasive prenatal testing by using fetal cell-free DNA in maternal plasma has the potential to generate misleading prenatal diagnoses without the observation of fetuses. However, no fetal diagnoses should be made without observing fetuses and we must not forget 'the fetus as a patient'.