Imaging description

A 37-year-old G2P1 white female presented for a fetal anatomic survey at 19 weeks 3 days gestational age. She had been previously seen by the Genetic Counseling Service to discuss prenatal diagnosis options due to maternal age. She chose to proceed with sequential screening by nuchal translucency and first and second trimester biochemical analysis. Results of the sequential screening were negative.

Fetal ultrasound images showed an abnormal triangular-shaped calvarium (Fig. 79.1a) which demonstrated deformity on compression by the ultrasound probe (Fig. 79.1b). The fetal chest was abnormally shaped, with irregular contour of the ribs (Fig. 79.1c). The fetal humeri and femora were extremely short, with the length corresponding to a 13- to 14-week fetus (Fig. 79.1d, e). The head circumference, by comparison, reflected the true gestational age of 19 weeks 3 days (images not shown). The findings were strongly suggestive of osteogenesis imperfecta (OI).

After genetic counseling the couple decided to undergo termination of the pregnancy. Tissue was sent for mutation analysis of the COL1A1 and COL1A2 genes.