Screening for effects of maternal age and birth order in a register of handicapped children

Summary Studies of effects of maternal age and birth‐order differences on the risk of handicapping conditions among children are described. Data were obtained by linking 4716 records of cases in the British Columbia Register of Handicapped Children and Adults born in the years 1953 to 1958, to birth registrations of the same children, using as controls all live births in the province over the same period. Only the broad categories of disease recognized by the International Classification have been considered in the present account. The Register was used to screen for examples of special risks to (1) offspring of very young mothers, (2) offspring of older mothers, (3) first‐born offspring, and (4) offspring of higher birth orders. Appropriate statistical analyses were used to ensure the detection and measurement of maternal age effects independent of an influence of birth order, and vice versa. The methods, both of obtaining data systematically and of analysis, serve to illustrate the kind of work that will be needed in the future if information on parental age and parity are to be used effectively to detect mutation in humans. I am indebted to Mrs Olwyn Tavendale who carried out all of the statistical calculations reported here (first by hand and again using the G20 computer), to Miss Martha Smith who wrote the computer program and did the record linkages by which information from the birth registration and handicap registration files was integrated, to Mrs Pamela Attree who wrote the ‘101 Simulator’ program which was used to produce the tabulations, and to Dr J. M. Kennedy who wrote the ‘Newstat’ program used for analysing the data. The project of which this study is a part has depended much upon the help and collaboration of A.E.C.L.'s Computation Centre, the British Columbia Vital Statistics Division, and the Health and Welfare Division of the Dominion Bureau of Statistics. Permission to use the handicap records in this study was obtained from the Health Branch, Department of Health and Welfare, Province of British Columbia. The permission was conditional upon strict observance of the oath of secrecy respecting the non‐statistical information contained in the records.