Effect of embryo removal on concentrations of progesterone and LH in the rabbit.

Embryos were removed by flushing the oviducts or uterine horns on Days 1, 2, 3, 4, 5, or 6 of pregnancy or pseudopregnancy. Progesterone profiles of pregnant, flushed pregnant, pseudopregnant and flushed pseudopregnant does were identical until Day 12 post coitum regardless of the day of flushing. After Day 12, the profiles of intact pregnant does were different from those of the other three groups (P less than 0.01). LH levels were low (less than 1 ng/ml) in all groups before and after surgery and there were no significant differences between treated and control rabbits. These data demonstrate that removal of embryos at any time before implantation results in progesterone levels identical to those of pseudopregnancy and does not alter serum LH levels.