Embryo development and zona-shedding in the ligated oviduct and contralateral uterine horn of non-lactating and lactating Mongolian gerbils (Meriones unguiculatus).

Within the same female, concurrent lactation had no apparent effect on the development and hatching of embryos artificially retained in the oviduct while effectively inhibiting zona shedding and implantation in the contralateral uterine horn. This result is believed due to a specific inhibitor(s) present in the uterine fluid or to physical constriction by the uterus. These extrinsic, maternal factors act either singly or in combination to influence the mature blastocyst.