30 Eeva Jalavisto 



favourable economic circumstances in the population studied 

 tend to eliminate the maternal age effects, which may explain 

 the discrepancy between earlier and more recent data. In 

 spite of the high social level of the family histories on which 

 this study is based they represent a population with a very 

 high mortality. It is quite obvious that if a maternal age 

 effect exists, it is never very pronounced. Therefore it is 

 easily understood that low mortality in favourable conditions 

 does not allow such small effects to manifest themselves. 

 Consequently recent population statistics in western "Welfare 

 States" can no longer be used for detection of maternal age 

 effects. However, there still exist countries with sufficiently 

 low standards of living for such studies. It would be interest- 

 ing to compare records from these countries with data from 

 countries with a high standard of living. 



Summary 



Parental age effects were studied in material comprising 

 17,986 cases collected from Scandinavian noble and middle- 

 class family histories. It was concluded that total expectation 

 of life is not suited for elucidation of such effects, because of 

 the necessarily extended period of observation with resulting 

 inconsistency of the data. Since, however, such calculation 

 made it probable that advanced maternal age had no effect on 

 deaths after the age of 15 years, the group of dead between 

 the ages of 20 and 29 could be used as indicative of the 

 frequency of births in different parental ages. When the dis- 

 tribution of dead during the first and second years was com- 

 pared to that in the 20-29 year group, a slight excess of infant 

 deaths during the first and second years of life was noted in 

 the highest maternal age group ( ^ 35 years). In the maternal 

 age group 25-29 years the relative number of infant deaths 

 was remarkably low, this maternal age being the most 

 favourable for the survival of the offspring. A similar com- 

 parison in the paternal series did not show any significant 

 paternal age effect on the survival of the progeny. 



