Temporal changes in Ohio amniocentesis utilization during the first twelve years (1972-1983), and frequency of chromosome abnormalities observed.

The history of amniocentesis utilization in the seventh largest state of the United States is documented from its inception in 1972 through the first half of 1984. Amniocentesis utilization ratios for Ohio residents aged greater than or equal to 35 have increased from 0.21 per cent (19/9091) in 1972 to 23.4 per cent (1655/7531) in 1983, representing an average annual growth rate of 43.1 per cent. Of the amniocenteses performed from January 1, 1978-July 1, 1984, 71 per cent were referred for advanced maternal age (greater than or equal to 35), 15 per cent for maternal anxiety (30-34), 10 per cent for family history or previous child with a genetic defect, and 4 per cent for other reasons. Between 1978-1983 utilization by women 45 years of age was only 20 per cent higher than women 35 even though their risk of giving birth to a Down syndrome child was bout one order of magnitude higher. In addition, various factors were tested as to whether they affected utilization of amniocentesis by women greater than or equal to 35 during 1978-1983. A strong correlation of +0.89 existed between county population size and utilization ratios. No difference in utilization was found between whites and nonwhites, regardless of county population size. When utilization ratios were compared separately between Protestants, Catholics and other religions in Ohio's most populated county, no statistical differences were found. From 1978-July 1, 1984, the frequency of all cytogenetically abnormal chromosome results observed in Ohio amniocenteses to women greater than or equal to 35 was 2.48 per cent (187/7536). Of these, 2.15 per cent (162/7536) had unbalanced karyotypes. Future maximum amniocentesis utilization for women greater than or equal to 35 is estimated at 60-70 per cent.