An abnormal head shape is an uncommon finding on prenatal ultrasound, associated most commonly with spina bifida, aneuploidy or oligohydramnios. In other cases diagnosis can be difficult. The objective of this study was to define management pathways for the investigation of fetuses with an abnormal head shape. Fetuses with an abnormal skull shape seen over a 10-year period in our unit were identified by searching the computerised database. Sonographic findings, diagnosis and outcome were reviewed. Three hundred and thirty-one cases were identified, the majority being associated with spina bifida (30%, lemon-shaped), aneuploidy (12%, strawberry-shaped) or dolicocephaly (18%) secondary to fetal position or oligohydramnios. Of the remainder, eight had craniosynostosis, three of which had a skeletal dysplasia. There was also one fetus each with Aperts syndrome, Saethre Chotzen syndrome and I-cell disease and two with an as yet undefined craniosynostosis sydrome.