Screening for fetal chromosomal abnormalities by maternal serum biochemistry and ultrasound examination of fetal morphology.

The failure of screening studies based on maternal age to reduce substantially the birth incidence of chromosomally abnormal babies has stimulated the search for new methods of screening. In this paper we review the latest literature on the two new approaches to screening for fetal chromosomal abnormalities: maternal blood analysis and examination of the fetal anatomy by ultrasound. Preliminary results from maternal serum biochemistry screening indicate that detection of trisomy 21 is significantly improved, and application of biochemical testing may be expanded to the first trimester of pregnancy. Findings from studies on the association between fetal malformations and chromosomal abnormalities indicate that a high percentage of fetuses with an abnormal karyotype can be detected by ultrasound. In order to improve the detection rate and counsel parents appropriately, prospective studies are needed to determine the sensitivity and specificity of different markers in unselected populations of all ages. Information from such studies will also help us to avoid unnecessary anxiety and keep the fetal loss rate due to invasive procedures as low as possible.