Delayed first injection of the once-a-month injectable contraceptive containing 25 mg of medroxyprogesterone acetate and 5 mg of E(2)-cypionate: effects on ovarian function.

Objective: To assess whether women who were administered the first injection of DMPA+E(2)C 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+E(2)C as their method of contraception.

Intervention(s): Participants received a DMPA+E(2)C 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+E(2)C 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+E(2)C 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+E(2)C 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.