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In summary, we found that the availability of genetic services for the Medicaid patients with the 11 selected disorders follow the general population distribution for Texas. In general, there is no major geographic factor limiting availability of services. We also found that the calculation of Medicaid dollars paid according to the size of the metropolitan area in which the patient resides indicates that there are fewer Medicaid dollars spent on these 11 genetic disorders per person in the population in the larger metropolitan areas. We conclude that preliminary review of these data indicate that the urban poor may have a greater need for medical services that deal with genetic disease.

Genetic counselling is recommended for parents of children with neural tube defects (NTDs) to inform them of the recurrence risks and the option of prenatal diagnosis. British Columbia provides an excellent site to examine the use by parents of genetic counselling services for NTDs. Genetic services for the entire province are centralized, and there is virtually complete ascertainment of all NTD births. The results from this study indicate that use of genetic counselling services is influenced by the type of NTD present and whether the index case was live or stillborn. Genetic counselling is most often sought after the birth of a liveborn infant with spina bifida.

The aim of this paper is to clarify some of the concepts used in the calculation of risk in genetic counselling. The use of probability as a measure of risk in a particular case is reviewed, with special reference to the Fisher-Neyman controversy. The technical concept of likelihood is then introduced and applied to risk probabilities themselves. The difficulties of interpretation are discussed, with a distinction drawn between calculating the risk for a child and inferring the genotype of his mother, even though the risk is wholly determined by the genotype. Fiducial inference is briefly mentioned, and the paper ends with a discussion of the problem which arises when the functional relationship between an unknown parameter and the unknown risk is not 1:1. The conclusion is tentatively reached that risk can only be gauged by probability and thus that prior probabilities must sometimes be assumed, but the paper is primarily intended as a guide and catalyst for the informed discussion of some of the difficulties, which may involve ethical dilemmas.