Since more and more women in developed countries are delaying childbearing to an older age, it is important to find out whether birth defects, other than those resulting from chromosomal anomalies, are related to maternal age. We have studied all 26,859 children with birth defects of unknown aetiology identified among 576,815 consecutive livebirths in British Columbia. All these cases' records were linked with provincial birth records to allow determination of maternal age at birth. We excluded children with chromosomal anomalies and those with other birth defects of known aetiology. Only 3 of the 43 birth defect categories studied showed significant maternal-age-specific trends: there were decreasing linear trends with maternal age for patent ductus arteriosus (chi 2 = 36.65, 1 df, p less than 0.01) and hypertrophic pyloric stenosis (chi 2 = 4.90, 1 df, p less than 0.05) and a bell-shaped curve (risk increasing to maternal age 30 then falling) for congenital dislocatable hip/hip click. The findings from this population-based analysis of no association between the incidence of birth defects of unknown aetiology and advancing maternal age should be reassuring to healthy women who opt to delay childbearing.
It has been suggested that older mothers are more likely to have a child with isolated cleft palate (CP) or cleft lip +/- cleft palate (CL +/- CP), but most of these studies have been based on fairly small sample sizes. Data from a population-based registry with multiple sources of case ascertainment were used to examine any association of maternal age with the incidence of these defects in infants without other congenital anomalies. The study group consisted of all cases with CP or CL +/- CP without other congenital anomalies from a series of over half a million consecutive livebirths during the period 1966 to 1981 inclusive in British Columbia. During the study period, the overall incidences of isolated CP and isolated CL +/- CP per 10,000 livebirths were 3.9 and 8.2, respectively. No association with maternal age was found when either isolated CP or isolated CL +/- CP was analyzed as a group. When analyzed by sex, and by CP or CL +/- CP, no significant maternal-age effect was observed for males and females with CP or CL +/- CP. Our population-based data, therefore, do not show that older mothers are more likely to have a child with cleft palate, or cleft lip +/- cleft palate.
Amniocentesis is now commonly used in many countries; it is important to know whether there are any long-term adverse effects on children born after this procedure, in particular disabilities that may emerge during childhood or adolescence. We studied consecutive liveborn offspring of women who had had amniocentesis and compared them with matched controls whose mothers had not had amniocentesis. The controls were matched for age of mother, residence by geographic health unit, sex, and when the birth occurred. 1296 cases and 3704 controls were studied. With the exception of one disorder, the offspring of women who had had amniocentesis were no more likely than controls to have a registrable disability (such as hearing disabilities, learning difficulties, visual problems, and limb anomalies) during childhood and adolescence. The follow-up period was 7-18 years. Children of women who had amniocentesis had a significantly higher rate of haemolytic disease due to ABO isoimmunisation than matched controls. The results of this study should therefore be reassuring to women having amniocentesis, and be useful to women making decisions about having this procedure.
Utilization of amniocentesis for prenatal diagnosis because of the indication of advanced maternal age (greater than or equal to 35 years at delivery) was examined in the population of B.C. over an 8-year period (1976-1983). As of 1983, approximately one out of three eligible women (greater than or equal to 35 years at delivery) is having the test. In the older group (greater than or equal to 38 years at delivery) approximately one out of two eligible women is having the test. The data do not indicate that the proportion of eligible women having amniocentesis has reached a plateau; utilization is continuing to increase. It appears that prenatal diagnosis is an ethically acceptable alternative for a large proportion of the population.