Trisomy 18 is the second most common trisomy syndrome. Sonographically, trisomy 18 syndrome can present with a wide range of fetal anomalies. The specific anomalies discussed in this report include choroid plexus cysts, agenesis of the corpus callosum, cleft lip, micrognathia, cystic hygroma, cardiac defects, diaphragmatic defects, omphalocele, spinal defects, and extremity defects. Knowledge of the abnormalities associated with trisomy 18 enhances the sonographer's ability to recognize this phenomenon when encountered.
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