Timing of onset of contraceptive effectiveness in Norplant implant users. Part I. Changes in cervical mucus.

ABSTRACT

PIP: To provide clinicians with evidence as to when the cervical mucus is hostile enough in new Norplant implant acceptors to indicate a contraceptive effect, 42 women requesting Norplant from clinical sites in Santo Domingo, Dominican Republic, and Baltimore, Maryland (US), in 1994-95 were enrolled in a clinical descriptive study. At baseline, when all women were between days 8 and 13 of their menstrual cycle, the median cervical mucus score was 6 ("fair") out of a possible maximum of 12. This score declined to 5 at 12 and 24 hours and continued to decrease through day 7, when it reached 2--a level judged hostile to sperm penetration. Overall, 73% of women had a "poor" cervical mucus score by day 3 and 90% were in this category by day 7. There were substantial drops in the overall median distance travelled by the vanguard sperm and in the percentage of subjects demonstrating poor sperm penetration after 12 hours for each cervical mucus score grouping. 91% of women had poor sperm penetration by day 3 and 93% by day 7. These findings suggest that backup contraceptive protection for the entire cycle after Norplant insertion--a standard recommendation--is not necessary given the profound effect of levonorgestrel on cervical mucus shortly after insertion, even in the event of possible ovulation.