[Sonomarkers: subtle ultrasound findings in the 20-week ultrasound examination, which have a low association with some chromosomal and non-chromosomal abnormalities in the fetus].

Currently all pregnant women residing in the Netherlands are offered second trimester ultrasound screening for the detection of fetal congenital structural abnormalities. This routine ultrasound examination takes place at 18 to 22 weeks' gestation. The ultrasound examination may yield soft markers, which are characterized by subtle morphological changes that are often transient and have little or no pathological significance. Soft markers are of interest because of their association with fetal congenital anomalies, in particular aneuploidy. This may create uncertainty for the pregnant woman and the care provider. Information can be found in the literature about the strength of the association of soft markers, when detected as an isolated finding, and the presence of fetal abnormalities. One or more soft markers are detected during routine ultrasound in approximately 5% of pregnant women. 4 markers (echogenic intracardiac focus, echogenic bowel, mild ventriculomegaly and shortened femur) are associated with Down syndrome. Given the low prevalence of Down syndrome in the general population and the relatively low strength of association with the syndrome, the positive predictive value of these markers is very low. The same is true for choroid plexus cysts, which are associated with trisomy 18. Apart from chromosomal abnormalities, some soft markers (echogenic bowel, mild ventriculomegaly and shortened femur) are also associated with non-chromosomal fetal abnormalities. Renal pyelectasis and the 2-vessel (instead of 3-vessel) umbilical cord are associated with non-chromosomal abnormalities only. It is recommended that pregnant women be informed about the nature and implications of these findings before the examination.