Sonographic Findings in Partial Type of Trisomy 18

Trisomy 18 (Edwards syndrome) is the second most common trisomy among live born fetuses, with poor prognosis. Estimate of its incidence is between 1 in 4000- 16000 live births. Most of the chromosomal abnormalities in fetuses are detected by prenatal ultrasound findings in the first and second trimesters. In this case re- port, we present a partial type of trisomy 18 occurring through de novo unbalanced translocation of chromosomes 18 and 21. The ultrasound features enabling the early detection of trisomy 18 include a delayed ossification of calvarium combined with early onset of fetal growth restriction (FGR) and the absence of nasal bone through performing triple test followed by amniocentesis. Finally, the parents decided to terminate the pregnancy.