Clinical study of a continuous daily micro-dose progestogen contraceptive--d-norgestrel

Effectiveness and efficacy rates of progestin-only pills: A comprehensive literature review

OBJECTIVES

To synthesize published literature on POP effectiveness and efficacy.

STUDY DESIGN

We searched PubMed Central, PubMed, and the Cochrane library through March 07, 2022. We included articles written in English reporting a Pearl Index or life table rate for pregnancy. We excluded articles only assessing formulations that: were never marketed globally, are only sold in combination with estrogen, are currently sold only for noncontraceptive purposes, or were not given to participants continuously. Four researchers independently extracted data and two analyzed data using Excel and R.

RESULTS

We included 54 studies. Among studies at low or moderate risk of bias, the median Pearl Index rate (the failure rate during typical use) was 1.63 (range 0.00-14.20, IQR 4.03) and the median method failure Pearl Index rate (the failure rate during perfect use) was 0.97 (range 0.40-6.50, IQR 0.68). Excluding the newer formulations, Desogestrel and Drospirenone, which are closer to combined oral contraceptives in that they prevent pregnancy by inhibiting ovulation, the median Pearl Index rate is 2.00 (range 0.00-14.12, IQR 2.5) and the median method failure Pearl Index rate is 1.05 (range 0.00-10.90, IQR 1.38).

CONCLUSIONS

Among studies at low or moderate risk of bias, the median Pearl Index rate during typical POP use was much lower than currently estimated (7.00), while the median perfect use rate was similar to current estimates.

IMPLICATIONS

Future research should investigate the possibility that POPs may be much more effective during typical use than currently believed.

A multicenter clinical trial of a progestin-only oral contraceptive in lactating women

A non-comparative study of a progestin-only oral contraceptive (POC) containing 75 micrograms norgestrel was conducted at 22 sites in 14 countries. This study was designed to evaluate safety, contraceptive efficacy, and the overall acceptability of a POC in breastfeeding women. A total of 4,088 women entered the study over a three-year period and 29,399 woman-months of experience was gathered. Women had follow-up visits at 2, 6, and 11 months after admission. Headaches and vaginal discharge were the medical complaints most commonly reported by women, both prior to and after admission. Menstrual problems were reported by 59% of the women after admission. Of the 3,714 women who returned for at least one follow-up visit, 1,101 (29.6%) discontinued through month 11. The 11-month total discontinuation percentage, including those lost to follow-up (25.3%) was 51.6%. The most common reason given for discontinuation was a woman's desire for a change in contraceptive method. Only 4.9% discontinued pill use for menstrual problems, a percentage far below those generally reported for POCs. Twenty-nine unintended pregnancies occurred through 11 months giving a gross cumulative life table rate of 1.2 per 100 women (Pearl Index = 1.4). The POC appears to be a safe, effective and acceptable contraceptive option for postpartum breastfeeding women.

The effect of daily d-norgestrel (30 micrograms) on serum progesterone in Thai women

Serum progesterone levels were measured by RIA in 23 Thai women during the first 3 of a 6-month treatment period of taking 30 micrograms d-Norgestrel daily and again for a 3-month period after discontinuing its use in order to determine the frequency of ovulation. During the period of use, 11 out of the 23 subjects showed no evidence of ovulation while only 1 subject failed to ovulate during the post-treatment stage. The median time for the post-treatment resumption of ovulation was 20 days with the earliest occurring before day 10 and the latest around day 85. The frequency of ovulation in women who did ovulate during the treatment period appeared to be depressed with an average of 1.8 ovulations/subject as compared to 2.4 during the post-treatment. Menstrual bleeding patterns were not significantly altered.