Corpus luteum--conceptus--follicle relationships during the fertile cycle in rhesus monkeys: pregnancy maintenance despite early luteal removal.

To determine how early in pregnancy cyclic follicle growth is interrupted, 6 pregnant monkeys were luteectomized (CLX) on day 29 or 30 of the cycle (approximately 1 week after implantation) to abbreviate the fertile cycle to approximately the length of nonfertile cycles. Unexpectedly, 3 of 6 monkeys remained pregnant despite early removal of luteal support. In the remainder, which aborted, the next ovulation was delayed beyond the interval typically observed after CLX in nonfertile cycles. Two of 4 other monkeys ovariectomized on day 29 also maintained their pregnancies. Our findings demonstrate that: 1) in 5 of 10 monkeys, the conceptus could survive without luteal support within a week after luteal rescue, and 2) secretion(s) of the conceptus also contribute to an arrest of cyclic follicle growth early in pregnancy.