Pregnant BALB/c mice were inoculated intravaginally on day 5 of gestation w
ith the Chlamydia trachomatis mouse pneumonitis biovar. Animals that receiv
ed 10(5), 10(6), or 10(7) inclusion-forming units (IFU) of C. trachomatis d
elivered prematurely on days 15 to 16 of gestation. A focal inflammatory in
filtrate was observed in the wall of the uterus on the day 14 of gestation
in animals inoculated with 105 IFU. In this group of mice, immunohistochemi
cal analysis showed chlamydial inclusions in the endometrium and fetal memb
ranes.