Isolated anomaly may not warrant invasive testing: midtrimester scan.(Obstetrics)

ATLANTA -- An isolated, subtle anomaly seen on a midtrimester ultrasound may be innocuous if the mother is not at high risk and the triple screen is normal.

But with advanced maternal age or if multiple abnormalities are present, an adverse outcome is possible and further diagnostic procedures are warranted, Dr. Ray O. Bahado-Singh said at a conference on high-risk obstetrics sponsored by Symposia Medicus.

A single umbilical artery, for example, has been reported to be associated with a whole range of gross anomalies, particularly cardiovascular, in 21%-76% of cases. Should this be seen on a screening ultrasound, therefore, a targeted ultrasound should be done to rule out a structural abnormality. A thorough heart examination also must be performed, and possibly a fetal echocardiogram, said Dr. Bahado-Singh, director of maternal-fetal medicine at the University of Cincinnati.

Karyotyping should be done if other anomalies are present. "And even if there are no structural abnormalities, it is not inappropriate to do a repeat ultrasound at 32-34 weeks, because there is a sense from the literature that a single umbilical artery is associated with fetal growth restriction."

Another perplexing ultrasound finding is that of an isolated choroid plexus cyst. Whether the presence of this anomaly increases the risk for aneuploidy--and whether karyotyping should be done--remains controversial.

"Obviously, in the presence of an associated structural defect, karyotyping is indicated," Dr. Bahado-Singh said. Otherwise, a targeted ultrasound ...