Timing of onset of contraceptive effectiveness in Depo-Provera users: Part I. Changes in cervical mucus.

ABSTRACT

OBJECTIVE: To evaluate the changes in cervical mucus within the first hours or days after depot medroxyprogesterone acetate (MPA) injection so as to estimate the time at which cervical mucus becomes hostile enough to prevent pregnancy. DESIGN: Multicenter, clinical descriptive study. SETTING: Family planning clinic. PATIENT(S) Thirty women who were between days 8 and 13 of their menstrual cycle and who had requested Depo-Provera were enrolled in the study. INTERVENTION(S) Cervical mucus and blood samples were obtained; transvaginal ultrasonography was performed. MAIN OUTCOME MEASURE(S) Cervical mucus scores, sperm penetration distances, ovarian follicular size, and serum levels of progesterone and estradiol. RESULT(S) From 6 to 24 hours after injection, there was a sharp decline in the cervical mucus score for most of the subjects. All subjects exhibited poor mucus on day 3 after injection, and by day 7, all subjects had zero scores, with the exception of two outliers on each day. Sperm penetration, as measured by the vanguard sperm distance, was already poor (< 1 cm) in 7 of the 30 subjects at the time of injection and was reduced progressively up to 24 hours after injection, when only four subjects had a sperm penetration of > 1 cm. A rapid decline in the estimated number of sperm was observed at 12 hours and more so at 24 hours in the majority of subjects. CONCLUSION(S) The data presented in this report confirmed that depot MPA causes profound changes in cervical mucus after injection. Although very little change was seen at 6 hours, alterations were observed subsequently, with 90% of the subjects showing a poor cervical mucus score 24 hours after administration of the progestin. No reliable clinical marker is available to identify in which women depot MPA might exert its effect on cervical mucus within 3 days. Thus, we believe that at present, women should be informed of this uncertainty and should use a backup method of contraception for 7 days when the first injection of depot MPA is provided after the seventh day of the menstrual cycle.

ABSTRACT

PIP More accurate knowledge of the time of onset of cervical mucus changes after Depo-Provera injection would enable family planning providers to counsel new acceptors to use a backup method only for the amount of time it is really needed. To obtain such data, 30 women from a family planning clinic in Campinas, Brazil, who requested Depo-Provera in 1995-96 were recruited. At baseline, 11 women had a poor cervical mucus score (0-4), 12 had a fair score (3-8), and 7 scored in the good range (9-12). Between 6 and 24 hours after injection, a sharp decline occurred in the cervical mucus score in all but 3 patients (each of whom had a "good" score at baseline). On day 3, 29 women had "poor" mucus and the remaining woman had a cervical mucus score in the fair range. By day 7, 29 women had zero mucus scores; the score in the last woman was 1. 24 hours after injection, sperm penetration (measured by vanguard sperm distance) had decreased to under 1 cm in all but 4 women. At day 3, 1 of the 2 women with good penetration at 24 hours maintained a vanguard sperm distance of 2.5 cm and an estimated sperm count of 15,363. By day 7, sperm penetration was zero in all but 1 woman (0.5 cm). These findings confirm that depot medroxyprogesterone acetate causes profound changes in cervical mucus after injection. The lack of a more complete hostility to sperm penetration at day 3 was unexpected, however. Given the nonavailability of a reliable clinical marker to verify a contraceptive effect at 3 days, it seems prudent to advise new Depo-Provera acceptors to use a backup method for the first 7 days.