Strawberry-shaped skull in fetal trisomy 18.

During an 8-year period, a strawberry-shaped skull (flattening of the occiput with pointing of the frontal bones), was observed in 54 (3%) of the 2,086 fetuses that underwent karyotyping in our unit because of fetal malformations and/or growth retardation. In all 54 cases with a strawberry-shaped skull, there were other fetal malformations; in 43 (80%) fetuses, there was trisomy 18 and in 1 triploidy. Therefore, the ultrasonographic finding of a strawberry-shaped skull should initiate a diligent search for the presence of other markers of trisomy 18 and is a strong indication for fetal karyotyping. However, in the total series of 2,086 fetuses with malformations and/or growth retardation, there were another 40 fetuses with trisomy 18 and 41 with triploidy who did not have a strawberry-shaped skull.