Sonographic diagnosis of caudal regression in the first trimester of pregnancy.

audal regression syndrome (CRS) represents a continuum of congenital anomalies that may include incomplete development of the sacrum and, to a lesser extent, the lumbar vertebrae, disruption of the distal spinal cord, and extreme lack of growth of the caudal region.1 First-trimester prenatal diagnosis of CRS is challenging because of incomplete ossification of the sacrum at that time.2 Most case reports of CRS have occurred during the second trimester.3–10 We report a case of CRS diagnosed during the first trimester on the basis of transvaginal sonography.