The cycle pregnancy rate is normal in baboons with stage I endometriosis but decreased in primates with stage II and stage III-IV disease

OBJECTIVES: To test the hypothesis that fertility is reduced in baboons with endometriosis. DESIGN: Prospective controlled follow-up study. SETTING: Institute of Primate Research, Nairobi Kenya. SUBJECTS: Seventy-one baboons, including 34 controls (normal pelvis) and 37 animals with histologically proven endometriosis (16 spontaneous and 21 induced). Baboons with endometriosis had minimal (n = 9), mild (n = 14), moderate (n = 7), or severe (n = 7) disease. INTERVENTIONS: Seventy-one baboons were mated during 286 cycles. MAIN OUTCOME MEASURES: Cycle fecundity rate, cycle pregnancy rate, cycle abortion rate. RESULTS: Cycle pregnancy rate (excluding spontaneous abortions) was 15% (44/286) and was comparable between controls (19%, 20/104) and baboons with endometriosis (13%, 24/182). The cycle pregnancy rates were 24%, 10%, 7.5%, and 12.5% in animals with minimal, mild, moderate, and severe endometriosis, respectively. The cycle pregnancy rate was significantly lower in baboons with stage III-IV endometriosis (9%, 6/64) and with stage II disease (10%, 7/73) than in animals with stage I endometriosis (24%, 11/45) or in controls with a normal pelvis (19%). CONCLUSION: The normal cycle pregnancy rate in baboons with stage I endometriosis and the decreased cycle pregnancy rate in baboons with stage II and stage III-IV disease suggest that fertility decreases with the stage of endometriosis in baboons.