The growing demand for midtrimester amniocentesis: a systems approach to forecasting the need for facilities.

A predicted shift in composition of the child-bearing population of the United States to higher maternal ages by year 2000 indicates that the number of chromosomally abnormal offspring of women age 35 and over will increase by 64% while the total number of women increases only 21%. We formulated a conceptual model of a health care system that predicts demand for amniocentesis from prospective patients in any particular region, the number of defective offspring detected, and the future cost of custodial care using any given level of detection effort. It was found that as capacity of clinic facilities and use by women age 35 and over in the area increased, the expenditure for amniocentesis combined with the cost of custodial care for undetected offspring decreased, assuming termination of affected pregnancies. Use of this model will enable health care managers to anticipate need for facilities, and also guide the formulation of social policy in the provision of new health services by enabling them to take into account the predictable effects of these services upon other public services.