Prenatal sonographic diagnosis of truncus arteriosus associated with holoprosencephaly.

We present the case of a truncus arteriosus associated with holoprosencephaly detected in a fetus in the first trimester and the sonographic findings that established this diagnosis. A physical exam was performed on a 35-year-old pregnant woman, gravida 2, para 1. At 20 weeks, sonography showed large-for-date uterine size. Fetal biometry was consistent with menstrual age. Amniotic fluid volume was elevated to 25 AFI cm. Fetal echocardiography revealed a single common artery arising from the heart, a ventricular septal defect, and other cardiac defects. Abnormalities of the fetal brain and face were also shown via sonography, including the presence of a common lateral ventricle without falx cerebri. Alobar holoprosencephaly, the most severe form of holoprosencephaly, was diagnosed. Prenatal chromosomal analysis was offered and the patient elected to have cordocentesis. The chromosome study was normal. Success in surgical repair of truncus arteriosus is established, but alobar holoprosencephaly is associated with neonatal death. Continuation of the pregnancy carried risks for the mother. After proper counseling, the parents of this fetus were offered and accepted termination of pregnancy. A male abortus weighing 320 grams was delivered. Postnatal findings and autopsy confirmed the diagnosis.