Paternal age in relation to selected birth defects.

The association between paternal age, within six maternal age categories, and malformations reported on birth certificates was studied in 776,642 white, single live births in Upstate New York (1968-73). The association between paternal age and total malformation rate was not statistically significant (chi-square test); in some maternal age groups, however, high malformation rates occurred in the older paternal age groups (55-59 or 60+ years). Specific defect categories with some evidence for dominant inheritance were analyzed separately. The only statistically significant association with paternal age was for syndactyly (chi-square test, p<.05), due largely to a largerthan -expected number of defects in 50-59 year-old fathers. A relatively high frequency of Polydactyly was evident in the 60+ year-old fathers (i.e., 4. 25 per 1,000, vs. 0.42 per 1,000 overall rate), but the overall association was not statistically significant. Some possible interpretations of the findings are discussed. Although maternal age has been studied extensively as a variable in relation to birth weight and birth defects, paternal age has received relatively little attention. Selvin and Garfinkel (1972) showed that paternal age, independent of maternal age and to some extent birth order, is significantly associated with the frequency of low birth weight. Selected birth defects have been studied with respect to paternal age. Milham and Gittelsohn (1965) reported no evidence for a paternal age effect on 10 selected birthdefect categories, but detailed data were not presented. From surgical records in Utah, Woolf (1963) reported evidence for a paternal age effect on cleft lip and palate, but the control group was recognized as not very appropriate. Other studies have provided evidence for an association between paternal age and certain defects related to dominant genes, as д-eviewed by Matsunaga (1973). Large samples sizes are needed to study the possible effects of paternal age, especially on birth defects that are relatively infrequent; also, such confounding variables as maternal age must be considered. The present study considers paternal age, within maternal age categories, in relation to 1Birth Defects Institute, State Department of Health, Albany, New York. Present address: Center for Human Radiobiology, Radiological and Environmental Research Division, Argonne National Laboratory, Argonne, Illinois, 60439. Human Biology , December 1976, Vol. 48, No. 4, pp. 727-739. ©Wayne State University Press, 1976. This content downloaded from 157.55. 39.210 on Sun, 31 Jul 2016 05:12:03 UTC All use subject to http://about.jstor. org/terms 728 Anthony P. Poledňak the frequency of reporting of one or more malformations, and selected malformations analyzed separately, in a sample of about 800,000 white, single live births. Subjects and Methods The original sample comprised 820,163 white, single live births recorded in upstate New York from 1968 to 1973. Analysis was limited to births with maternal age of 15-49 years. Paternal age was reported in 776,642 of the remaining births; 42,648 births with paternal age not reported (i.e., out-of-wedlock births) were excluded from analysis. Only the first two malformations, if any, reported on the certificate were coded and available for analysis. The system of coding malformations was that of Milham (1963). A large number of types of defects are coded, but "major" defects (central nervous and cardiovascular system defects, oral clefts, clubfoot, defects of the skeleton and external genitals, etc.) comprise the majority (Gittelsohn and Milham, 1965). Within six maternal age categories, the total malformation rate (i.e. , the proportion of birth certificates with mention of at least one defect) was determined by paternal age category (15-19, 20-24, . . .to 60+ years). This analysis would indicate whether or not there is a general tendency for paternal age to be associated with frequency of birth defects (i.e., major defects reported on certificates). By way of analogy, malformation rates are generally higher at the extremes of the maternal age range. It is recognized, however, that different types of paternal age associations may exist for specific defects, so that such an overall analysis is of limited value. The defect categories selected for separate analysis were syndactyly, Polydactyly, oral clefts (cleft lip and/or cleft palate), and club foot. These were selected because of their more complete reporting on birth certificates, relative to other defects, and because of evidence for dominant inheritance for at least some subtypes of each defect category. The association between paternal age and each defect category was assessed by a chi-square test of the frequency distributions; rates are also presented for comparison purposes. For defect categories showing statistically significant maternal age associations, separate chi-square tests were performed on frequencies by paternal age within each maternal age category. Numbers were small for some paternal age groups. Thus, adjacent columns were sometimes amalgamated. The general rule followed was that, in a large table, not more than one cell in five should have an expectation of less than This content downloaded from 157.55. 39.210 on Sun, 31 Jul 2016 05:12:03 UTC All use subject to http://about.jstor. org/terms Paternal Age and Birth Defects 729 five, and that a minimum expectation of one is permissable in each such cell (Hill, 1971: p. 160).