Potential Fetal Anomalies
Potential Fetal Anomalies missed at the 19 week ultrasound
Fetal anomaly scans at about 19 weeks of gestation are often thought by patients to exclude all major fetal anomalies. However this is not the case: for example it has been noted that up to 50% of congenital heart malformations are missed (RADIUS Study) in this way. Another example of this was a Dutch study of over 5,000 patients scanned between 16 and 24 weeks. Those skilled sonologists and sonographers missed 10 major and 42 minor congenital heart malformations on the basis of a normal 4 chamber view of the fetal heart. Only 7 fetuses had an abnormal 4 chamber view and of those only 2 had congenital heart disease.
Hydrocephaly often does not become apparent until 16 to 18 postmenstrual weeks or later. If one were to rely on a morphology scan to identify Down syndrome then 50% would be missed.
Specific serious anomalies which may be missed include:
- Hypo-plastic left heart syndrome
- neuronal migration disorders such as cortical dysplasia: a cause of intractable epilepsy
- hydrocephaly caused by such problems as aqueduct stenosis, Dandy Walker syndrome, absent corpus callosum
Some interest is focussed presently on the demonstration of intracranial translucency (which is found parallel with nuchal translucency). Its absence may suggest open spina bifida because of commonly associated changes in the fourth ventricle (Arnold Chiari malformation)