Improving the ultrasound detection of isolated fetal limb abnormalities.

Objective: The prenatal detection rate of isolated fetal limb abnormalities ranges from 4 to 29.5%. Our aim was to determine the accuracy of a detailed ultrasound protocol in detecting isolated fetal limb abnormalities Methods: This is a retrospective study of infants born at our institution with isolated limb defects from 2009 to 2014. Antepartum and postpartum records were reviewed for genetic testing results. We routinely image both upper and lower extremities, including all long bones, hands, feet, fingers and toes. Posturing, muscular tone and movement are also noted.

Results: During the study period, there were 52 neonates born with isolated fetal limb abnormalities who had received a fetal anatomic survey in our ultrasound unit and 15 930 sonograms performed with normal findings; 36 out of the 52 had been prenatally diagnosed (detection rate 69%). The specificity of the protocol was 100% as there were no false positive cases, the positive predictive value was 100% and negative predictive value 99.8%. Forty-three of 52 neonates had normal genetic testing either prenatally or postnatally; 9 neonates did not undergo genetic testing. The average additional time required for this detailed protocol was <5 min for second trimester sonogram.

Conclusion: A minimal investment in time for detailed evaluation of fetal limbs more than doubles the previously reported prenatal detection rate.