Follow-up sonograms for fetal growth evaluation turn up other problems

Doing full fetal anatomical surveys during follow-up exams of low-risk pregnancies can identify unanticipated fetal anomalies, particularly if the exams are intended to monitor fetal growth.

Dr. Eugene C. Toy and colleagues in the obstetrics and gynecology department at the Methodist Hospital in Houston published their research in the Sept. 26 issue of the Journal of Ultrasound in Medicine. They studied charts at a low-risk maternity clinic between July 1, 2005, and June 30, 2006, from women who had at least one ultrasound examination after 18 weeks' gestation with a complete and normal fetal anatomic assessment and at least one follow-up sonogram. Regardless of the reason for the follow-up exam, full fetal anatomic surveys were performed on each one.

A total of 4269 ultrasound examinations were performed in this time period, but only 437 (10.2%) were follow-up studies and 101 of these were excluded because the first exam showed a suspected fetal anomaly. Another 42 exams were excluded for other reasons. This left 294 women whose follow-up sonograms were studied.

Unanticipated fetal anomalies were found in 21 (7.1%) of these follow-up exams. The anomaly found most often was renal pyelectasis, and sonograms repeated to evaluate fetal growth yielded the most anomalies of any kind. Of the 122 women who had exams to evaluate fetal growth, 15 sonograms (12.3%) showed a fetal anomaly. Of the 172 exams conducted for other reasons, only six sonograms (3.5%) showed an unexpected anomaly.

"The point is not necessarily to do more follow-up sonograms," Toy said, "but rather to do full fetal anatomical surveys when follow-up sonograms are done."

To evaluate the severity of the problems, the researchers identified those mothers in the study who required neonatal interventions, defined in this study as surgical or medical therapy or follow-up with a subspecialty specifically for the suspected fetal anomaly. Of the six patients whose follow-up exams for reasons other than fetal growth evaluation showed anomalies, none had neonatal interventions. However, six of the 15 anomalies (40%) identified from fetal growth evaluations were addressed through neonatal intervention.

The researchers concluded that a complete fetal anatomic survey on follow-up sonograms may identify unanticipated fetal anomalies, especially when those exams are being performed to evaluate fetal growth.

"Our experience is that the fetal anatomical survey adds only 3.5 minutes - thus adding minimal extra cost and effort," Toy said.