The effect of maternal age on ovulation, corpora lutea of pregnancy, and implantation failure in mice.

Summary. C57B1 female mice aged 4 to 7 months (controls) and 8 to 9, 10 to 11, 12 to 13, and 14 to 15 months were mated and killed at 12 hr, 60 hr or 7\m=1/2\ days post coitum (p.c.). Corpora lutea were counted and evaluated in serially sectioned ovaries. Implantation sites were counted in the animals killed 7\m=1/2\ days p.c. The mean number of implantations in 10- to 11-month-old mice was less than in the control animals. This decrease was closely associated with morphological degeneration of corpora lutea of pregnancy. By 12 to 13 months of age most animals had neither implantation sites nor recognizable corpora lutea of pregnancy 7\m=1/2\ days after mating. These two changes were highly correlated and were not due to a decrease in the number ofovulations as determined by examina-tion of the ovaries of animals killed 12 or 60 hr p.c. It was concluded that the initial decline in fertility with increased maternal age in this strain of mouse may be due support