Experimentally induced endometriosis in rats: effect on fertility and the effects of pregnancy and lactation on the ectopic endometrial tissue

OBJECTIVE: To investigate the repercussion of experimentally induced endometriosis on the fertility of Wistar rats and the effects of pregnancy and lactation on endometrial ectopic implants. DESIGN: Eight-five animals were used for the experiment. Experimental endometriosis was induced in 44 and the remaining 41 were sham-operated (control group). After evaluating the growth of the implants in a second laparotomy, all the animals were mated until finding sperm in vaginal smears. In third and fourth laparotomies during pregnancy and lactation, pregnancy rate was determined, and the implants were re-evaluated, being resected for histological study. Serum estradiol (E2) and progesterone (P) levels were also measured. RESULTS: The pregnancy rate in animals with endometriosis was 65.7% versus 100% in control group. No statistical differences in days of gestation and number of pups were found between the two groups. Ectopic implants underwent a significant regression during lactation period. Serum E2 and P levels and histological features sustained these findings. CONCLUSION: Experimentally induced endometriosis diminishes pregnancy rate in rats. It is not pregnancy, but the anestrus condition created by lactation that exerts a beneficial effect on experimentally induced endometriosis in rats.