Sirenomelia Apus after Trimethoprim Exposure: First-Trimester Ultrasound Diagnosis-A Case Report

We report the early prenatal ultrasound diagnosis of sirenomelia apus at 12+4 weeks in a patient with trimethoprim exposure in the vulnerable period. First-trimester scan revealed a malformed fetus with one femur, one small tibia, no feet, intraabdominal unilocular cystic structure, and two-vessel umbilical cord with allantoic cyst. Ultrasound visualization with two/three/four-dimensions was helpful in the process of parental counseling. (c) 2012 Wiley Periodicals, Inc. J Clin Ultrasound, 2012;