Objective: To assess whether women who were administered the first injection of DMPA+E2C on day 7 of their menstrual cycle (delayed injection) exhibit the same degree of ovarian suppression as women who receive it on day 5 of their menstrual cycle. Design: Multicenter, randomized controlled trial.Setting: Reproductive health clinics. Patient(s): Women aged between 18 and 38 years (inclusive) willing to use DMPA+E2C as their method of contraception. Intervention(s): Participants received a DMPA+E2C injection on day 5 (control group, n = 41) or day 7 (delayed-injection group, n = 117) of their menstrual cycle. Main Outcome Measure(s): Ovarian activity and follicular development determined by serial serum progesterone levels and vaginal ultrasound. Result(s): Participants who received DMPA+E2C on day 5 of their menstrual cycle (control group) exhibited no more than limited follicular growth (no follicle >16 mm). Of those women who received DMPA+E2C on day 7 of their menstrual cycle (delayed-injection group), 21 (18%) showed some follicular growth, of whom 4 (3%) ovulated. Conclusion(s): The first injection of DMPA+E2C given on day 7 of a menstrual cycle does not provide the same inhibition of ovarian activity as that observed when it is administered on day 5 of the menstrual cycle. Copyright © 2001 American Society for Reproductive Medicine.754744748Hall PE, Task Force on Research on Introduction and Transfer of Technologies for Fertility Regulation, Special Programme of Research, Development and Research Training in Human Reproduction, World Health Organization, Geneva, Switzerland. The introduction of Cyclofem into national family planning programmes: experience from studies in Indonesia, Jamaica, Mexico, Thailand and Tunisia. Contraception 1994;49:489-507Hall, P., Bahamondes, L., Diaz, J., Petta, C., Introductory study of the once-a-month, injectable contraceptive Cyclofem in Brazil, Chile, Colombia, and Peru (1997) Contraception, 56, pp. 353-359Technical Guidance/Competence Working Group (TC/CWG). Recommendations for updating selected practices in contraceptive use. World Health Organization/USAID, 1997Ritchie, W.G., Ultrasound in the evaluation of normal and induced ovulation (1985) Fertil Steril, 43, pp. 167-181Brache, V., Alvarez, F., Faundes, A., Cochon, L., Thevenin, F., Effect of preovulatory insertion of Norplant implants over luteinizing hormone secretion and follicular development (1996) Fertil Steril, 65, pp. 1110-1114Garza-Flores, J., Rodriguez, V., Perez-Palacios, G., Virutamasen, P., Tang-Keow, P., Konsayreepong, R., A multicentered pharmacokinetic, pharmacodynamic study of once-a-month injectable contraceptives. I. Different doses of HRP112 and of DepoProvera. World Health Organization Task Force on Long-acting Systemic Agents for Fertility Regulation (1987) Contraception, 36, pp. 441-457Petta, C.A., Faundes, A., Dunson, T.R., Ramos, M., DeLucio, M., Faundes, D., Timing of onset of contraceptive effectiveness in Depo-Provera users. II. Effects on ovarian function (1998) Fertil Steril, 70, pp. 817-820Speroff, L., Glass, R.H., Kase, N.G., (1994), p. 191. , Clinical gynecologic endocrinology and infertility, Baltimore, MD: Williams and WilkinsBrache, V., Blumenthal, P.D., Alvarez, F., Dunson, T.R., Cochon, L., Faundes, A., Timing of onset of contraceptive effectiveness in Norplant implant users. II. Effect on the ovarian function in the first cycle of use (1999) Contraception, 59, pp. 245-251Jordan, J., Craig, K., Clifton, D.K., Soules, M.R., Luteal phase defectthe sensitivity and specificity of diagnostic methods in common clinical use (1994) Fertil Steril, 62, pp. 54-62Garza-Flores, J., Sang, G.W., Hall, P.E., Population and delivery systemsvariability in pharmacokinetics of long-acting injectable contraceptives (1994), pp. 69-83. , Snow R., Hall P.E. (Eds.), Steroid contraceptives and women's response. Regional variability and side-effects and pharmacokinetics, New York: Plenum Press