The objectives of this study were to assess whether women who were administered the first injection of the once-a-month contraceptive containing estradiol cypionate and 25 mg depot-medroxyprogesterone acetate (MPA+E2C) on Day 7 of their menstrual cycle (delayed injection) exhibit the same degree of cervical mucus changes as women who receive it on Day 5 of their menstrual cycle. This was a multicenter, randomized, controlled clinical trial. A total of 158 women, aged between 18 and 38 years (inclusive), who, were willing to use MPA+E2C as their contraceptive method participated in the trial. Participants received a MPA+E2C injection on Day 5 (control group, n = 41) or Day 7 (delayed-injection group, n = 117) of their menstrual cycle. Participants who received MPA+E2C on Day 5 of their menstrual cycle (control group) exhibited fair or poor mucus quality and poor sperm penetration. Of those women who received MPA+E2C on Day 7 of their menstrual cycle (delayed-injection group), 3 (3%) showed good mucus or good sperm penetration at some time point during follow-up. It is possible to conclude that the first injection of MPA+E2C given on Day 7 of a menstrual cycle does not provide the same degree of inhibition of mucus quality and sperm penetration as that observed if it is administered on Day 5. However, the theoretical risk of pregnancy after receiving MPA+E2C on Day 7 would be expected to be low. (C) 2002 Elsevier Science Inc. All rights reserved.646363368