3-D fetal ultrasound can help with counseling.(Obstetrics)

KAILUA KONA, HAWAII -- Three-dimensional ultrasound is less helpful for diagnosing fetal abnormalities than for counseling patients, Dr. Dolores H. Pretorius said at a conference on obstetrics, gynecology, perinatal medicine, neonatology, and the law.

Always performed as an adjunct to two-dimensional prenatal ultrasound, never as a replacement for it, 3-D ultrasound can help visualize and evaluate certain fetal abnormalities, give clinicians more confidence about what they're identifying, and help explain the problem to patients, she said.

Rarely does 3-D ultrasound identify additional abnormalities, said Dr. Pretorius, professor of radiology and director of imaging at the University of California, San Diego.

The most helpful medical use of 3-D ultrasound may be for imaging facial anomalies, especially small cleft lips and cleft palates that are difficult to see with 2-D ultrasound, according to a 2005 consensus panel convened by the American Institute of Ultrasound in Medicine.

Because 3-D ultrasound can provide consistent symmetrical views, unlike 2-D ultrasound, it may help diagnose micrognathia (small chin), but further research is needed to confirm that, she said at the conference, which was sponsored by Boston University. It also may be helpful for imaging brain and spinal anomalies, identifying sutures on the fetal skull, and for research studies of cardiac anomalies, the consensus panel suggested.

Anomalies of the ear or the extremities can be seen with 3-D ultrasound. A diagnosis of club feet by 3-D ultrasound is false 12%-22% of the time, however, so patients must be warned of the false-positive rate, she cautioned. "We've had patients terminate the pregnancy for club feet and then have normal feet at autopsy."

Referrals to check for central nervous system anomalies include cases of craniosynostosis or of mild ventriculomegaly, to look for the corpus callosum. A 3-D ultrasound of a neural tube defect can localize the level of the defect. "Most of the time this does not impact patient care" except when surgical ...