Aging and uterine growth during implantation in C57BL/6J mice

Uterine growth during implantation was compared in C57BL/6J mice aged 3-7 mo vs. 11-12 mo. All mice had given birth to at least one previous litter. Older mice had smaller uteri during early gestation (3 to 10 days post coitum) as measured by DNA content, although wet weight and protein were generally similar in both age groups. However, there were no age effects on uterine growth during implantation, as measured by the increments of DNA, as well as protein and wet weight per implantation site (decidual swelling) on days 6-10. These data are discussed in terms of the major increase in fetal death and resorptions in older mice subsequently observed by day 12-13. Larger age-related impairment of the artificially-induced decidual response is also considered. We conclude that impairments of the artificially induced decidual response do not predict the extent of decidual responses during pregnancy in aging mice.