Prenatal ultrasound findings in hydrolethalus: continuing difficulties in diagnosis.

We present the prenatal ultrasound findings in a case of hydrolethalus. This case illustrates ongoing problems in differentiating hydrolethalus, both pre- and postnatally, from other midline malformation syndromes including Pallister-Hall, Smith-Lemli-Opitz, pseudo-trisomy 13, oral facial-digital syndrome, and Meckel syndrome. Hydrolethalus can also be difficult to distinguish from certain skeletal dysplasias such as the short rib-polydactyly syndromes and campomelic dysplasia. Tests which can aid in diagnosis are presented.