Prenatal diagnosis of structural abnormalities.

In the past year, improved ultrasonographic quality has allowed the imaging of more and more subtle anomalies. A major focus of recent discussion, ie, whether the combination of ultrasonographic and maternal blood test results (eg, serum alpha-fetoprotein level) is a satisfactory screening method for commonplace anomalies such as Down's syndrome or spina bifida, is reviewed. Whether these noninvasive tests need to be supplemented by amniocentesis is also discussed, as are ultrasonographic markers for various trisomy syndromes and the association between renal abnormalities and chromosomal defects.