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Prolonged Use of the Etonogestrel Implant and Levonorgestrel Intrauterine Device - Two Years Beyond FDA-Approved Duration
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Design
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Ongoing prospective cohort study
N= 787
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Objective
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To evaluate the effectiveness of the contraceptive implant and the 52-mg hormonal intrauterine device (IUD) in women using the method for two years beyond the current FDA-approved duration
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Study Groups
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Implant (n= 291)
IUD (n= 496)
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Inclusion Criteria
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Women between the ages of 18 and 45 years of age, English or Spanish-speaking, sexually active with a male partner, not interested in conception in the next 12 months, willing to continue to use of their subdermal implant or levonorgestrel (LNG) IUD for a minimum of an additional one year, had to present within 3 months of the current FDA-approved duration of use (e.g. for implant: 33–39 months of use; 57–63 months of use for LNG IUD)
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Exclusion Criteria
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Not disclosed
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Methods
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Enrollment involves women who have utilized either the contraceptive implant or the 52-mg levonorgestrel IUD for at least 3 and 5 years, respectively. The initiation of IUD should be in 2007 or later, while the implant should have been started in 2009 or later. Demographic and reproductive health histories, along with objective body mass index (BMI) data were collected. Periodic venipuncture for the analysis of serum etonogestrel levels was offered to implant users.
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Duration
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January 2012 to July 2016
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Outcome Measures
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Primary: unintended pregnancy rates
Secondary: quantification of serum ENG levels at various time points during prolonged use of the implant and comparison of ENG levels across body mass index (BMI) classes
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Baseline Characteristics
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Implant (n=291)
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IUD (n=496)
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p-value |
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Age, years
18–22
23–29
30–34
35–45
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30.9%
47.4%
11.3%
10.3%
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1.4%
37.5%
28.2%
32.9%
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< 0.001 |
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Race
Black
White
Other
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70.4%
21.6%
7.9%
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51.4%
43.9%
4.7%
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< 0.001 |
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Ethnicity
Hispanic
Non-Hispanic
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4.5%
95.5%
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2.6%
97.2%
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0.16 |
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Low socioeconomic status **
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59.1% |
39.4% |
< 0.001 |
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Gravidity
0
1-2
3 or more
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28.7%
44.3%
27.0%
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29.6%
38.0%
32.4%
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0.16 |
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BMI
Less than 25
25–30
30 or higher
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25.1%
23.0%
51.9%
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32.8%
21.5%
45.7%
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0.07 |
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** Low socioeconomic status is defined as any participant reporting difficulty paying for basic needs such as food shelter or childcare or receiving public assistance.
Patients with higher BMIs were more likely to be older (p = 0.02), to have higher gravidity (p <0.01), and to be of lower socioeconomic status (p <0.01).
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Results
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Endpoint
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Implant (n=291)
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IUD (n=496)
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Confidence interval (CI)
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Completed women-years of follow-up
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444.0 |
696.9 |
-- |
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Documented pregnancies during the follow-up
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0 |
2 |
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Failure rates
Fourth years
Fifth years
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0
0
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-- |
One-sided 97.5% CI 0 to 1.48 per 100 woman years
One-sided %97.5 CI 0 to 2.65 per 100 women years
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Failure rates
Sixth year (1 year post-expiration)
Seventh year (2 year post expiration)
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--
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0.25
0.43
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95% CI 0.04 to 1.42 per 100 women years
95% CI 0.08 to 2.39 per 100 women years
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Etonogestrel level among implant users, pg/mL
At the time of method expiration
At the end of the fourth year
At the end of the fifth year
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207.7 (range 63.8 - 802.6)
166.1 (range 25.0 – 470.5)
153.0 (range 72.1–538.8)
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-- |
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| BMI-specific comparisons of median ENG levels were conducted at each time point. At the conclusion of four years of use, a statistical distinction emerged, revealing that overweight women exhibited the highest serum ENG (195.9 pg/ml: range 25.0–450.5) compared to normal (178.9 pg/ml: range 87.0–463.7) and obese (137.9 pg/ml: range 66.0–470.5) women (p=0.04). |
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Adverse Events
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N/A
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Study Author Conclusions
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This study indicates that the contraceptive implant and 52-mg hormonal IUD continue to be highly effective for at least two additional years of use. Serum etonogestrel evaluation demonstrates median levels remain above the ovulation threshold of 90pg/ml for women of in all BMI classes.
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InpharmD Researcher Critique
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One limitation involves the use of self-reporting to document contraceptive failures. While efforts were made to validate positive reports whenever feasible, the presence of social desirability bias might contribute to potential under-reporting of unintended pregnancies by women. The study is further limited by a small number of ENG samples at the five-year mark of implant use, potentially impacting the ability to detect subtle BMI differences.
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