Low-dose antiprogestin treatment prevents pregnancy in rhesus monkeys and is reversible after 1 year of treatment

S. M. Borman, K. M. Schwinof, C. Niemeyer, K. Chwalisz, Richard Stouffer, M. B. Zelinski-Wooten

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Background: Administration of low doses of an antiprogestin to rhesus monkeys permits ovarian/menstrual cyclicity, suppresses endomaterial proliferation and prevents pregnancy without adverse or toxic side-effects after 5-6 months of daily treatment. The purpose of this study was to test reversibility with respect to restoration of fertility after 1 year of low-dose antiprogestin treatment. Methods: This experiment included a daily 1 year vehicle- or antiprogestin-treatment interval followed by a 9 month post-treatment interval for adult, female rhesus monkeys (n = 5/group) of proven fertility and exhibiting regular menstrual cycles. Co-habitation occurred with a male of proven fertility and vaginal swabs were taken to identify the presence of sperm during the treatment (antiprogestin females) and post-treatment intervals (vehicle and antiprogestin females). Results: Mating and vaginal sperm were evident in all antiprogestin females during, and, in both groups, after treatment. Based on ultrasonography, none of the antiprogestin-treated females became pregnant during the treatment interval. However, upon cessation of treatment, pregnancy rates were similar between antiprogestin-treated (3/5) relative to vehicle-treated (4/5) females with live, healthy infants born in both groups. There were no differences between groups in fetal measurements, gestation lengths, live birth rates and infant weights. Conclusions: The reversal of the anti-fertility effects of chronic, low-dose antiprogestin treatment supports the clinical feasibility of potent and selective antiprogestins as potential contraceptives for women.

Original languageEnglish (US)
Pages (from-to)69-76
Number of pages8
JournalHuman Reproduction
Issue number1
StatePublished - Jan 1 2003


  • Antiprogestin
  • Contraception
  • Pregnancy
  • Reversibility
  • ZK 137 316

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology


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