Non-surgical uterine flushing for the recovery of preimplantation embryos in rhesus monkeys: Lack of seasonal infertility.

A non-surgical uterine flushing technique was employed to recover rhesus monkey preimplantation embryos during April--September, a period thought to be associated with reduced fertility. A total of 22 females of proven fertility, maintained indoors under strict light and temperature control, were employed for the study in which 72 menstrual cycles were monitored. The average length of their menstrual cycle was 27.9 ± 3.8 days. The percentages of cycles that showed normal cyclic patterns of estrogen, LH, and sex-skin color were 84.7%, 91.7%, and 90.3%, respectively. Following natural mating, uterine flushing was performed on days 4-7 of pregnancy. Of 58 attempts, 27 (46.6%) resulted in the recovery of embryonic materials. Two recoveries produced unfertilized oocytes; 20 yielded embryos which were morphologically normal, and 7 yielded damaged and/or degenerate embryos. Luteal function in cycles involving uterine flushings was evaluated by examining ovaries by laparoscopy, ovulation being confirmed in 34 of 35 examinations. Serum progesterone was > 2 ng/ml in 39 of 45 cycles. The conception rate of 46.6% noted in this study was similar (P > 0.4) to those observed from other natural matings in our colony, either during the same period (49.3%; n = 67) or during October--March (46.9%; n = 113). These results show that rhesus monkeys, maintained under appropriate environmental conditions, can experience normal fertile menstrual cycles throughout the summer months, and extend previous observations to demonstrate, for the first time, that preimplantation embryos can be recovered from this species year-round. © 1993 Wiley-Liss, Inc.