Trisomy 13 syndrome: prenatal US findings in a review of 33 cases.

PURPOSE: To determine the type and prevalence of prenatal ultrasound (US) findings in fetuses with trisomy 13. MATERIALS AND METHODS: Prenatal US findings in 33 consecutive fetuses with trisomy 13 and in 200 karyotypically normal fetuses were reviewed and compared. RESULTS: One or more abnormalities were found in 30 fetuses (91%). Major anomalies detected by means of US included holoprosencephaly (13 39%) or other central nervous system anomalies (19 58%), facial anomalies (15 48%), and renal (11 33%) and cardiac (16 48%) defects. Growth retardation was also present in 16 (48%). Echogenic chordae tendineae were seen in 10 (30%), which includes seven (39%) of 18 fetuses examined before 20 menstrual weeks (compared with four 2% of 200 fetuses in the reference group P < .001). Other findings not generally associated with trisomy 13 but present in this series included a large cisterna magna (six 18%), mild cerebral ventricular dilatation (three 9%), nuchal thickening or cystic hygroma (seven 21%), and a hypoplastic left side of the heart (seven 21%). CONCLUSION: Prenatal US can help detect one or more anomalies in most fetuses with trisomy 13; thus, US finding can indicate whether karyotype should be tested.