An epidemiological study of holoprosencephaly from a regional congenital anomaly register: 1995-2004

Adequate contemporary information to counsel patients with a prenatal diagnosis of holoprosencephaly is lacking. We addressed this using data from the West Midlands Congenital Anomaly Register (WMCAR), a population-based malformation register, during a time where technological improvements have been stable and anomaly screening is well established.

Cases were defined using the ICD 10 code for holoprosencephaly. Cases of livebirths, stillbirths and termination at all gestations were included in the study. The diagnosis was verified by a pathology or definitive radiological report with cross validation from the regional pathology, clinical genetics, cytogenetics and fetal medicine databases.

There were 113 cases reported of holoprosencephaly for the years 1995-2004. This represents a prevalence of 1.7 per 10,000 births and terminations, with no change in prevalence over time. There was a decreased risk of holoprosencephaly in the white population [white vs. nonwhite; RR 0.53(0.36-0.79)]. Karyotypical abnormality was noted in 46% of cases where the karyotype was known. Trisomy 13 was the most common chromosomal abnormality. Correct allocation of a diagnosis of holoprosencephaly by ultrasound occurred in 77% of cases, with another 12% having a severe intracranial abnormality but was not reported as holoprosencephaly. In 4%, a prenatal diagnosis of holoprosencephaly was not made. Termination of pregnancy was performed in 80% of all cases.

Holoprosencephaly is a morbid condition associated with significant secondary etiologies.