5.4 Effect of the Certainty of Diagnosis on Coding
Prenatal and postnatal diagnosis
The certainty of a diagnosis can vary for live births and fetal deaths (stillbirths), as well as when the diagnosis is prenatal only or postnatal. With pregnancy terminations, a prenatal diagnosis may not be verified for many reasons, including the method of termination, the condition of the specimen, or a lack of post-termination examination or autopsy. Programmes that are interested in more detailed information on inclusion of prenatal diagnosis in congenital anomaly surveillance can find some useful and practical suggestions and tips in the guidelines developed by the NBDPN in the USA (14). Among liveborn neonates who die shortly after birth, the diagnosis could also cause difficulties if certain examinations (e.g. X-rays and karyotyping) or an autopsy are not done.
Coding possible and confirmed diagnoses
When the diagnosis is uncertain (e.g. hydrocephalus suggested by prenatal ultrasound, but for which no postnatal confirmation is done), it is beneficial to distinguish possible diagnoses from confirmed diagnoses. This can be done by using a separate field on the congenital anomalies abstraction form to include this information (see Appendix G), or adding an extra digit to the ICD-10 codes, which has been done by some surveillance programmes (34).