Are There Two Maternal Age Groups In Down's Syndrome?
P. A. P. MORAN 1
1 Professor of Statistics, Institute of Advanced Studies, Australian National University, P.O. Box 4, Canberra, Australia
It is shown that the fact that the maternal age distribution of mothers of patients with Down's syndrome shows bitangentiality and occasionally bimodality does not necessarily imply that there are two different classes of causes operating of comparable frequency in the manner postulated by Penrose and Smith (apart from a small group which does not give a maternal age shift). The establishment of the existence of two such classes must await further investigation.
Submitted on July 20, 1973
