The Etonogestrel Contraceptive Implant and Obesity
Abstract & Commentary
By Rebecca H. Allen, MD, MPH, Assistant Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Providence, RI, is Associate Editor for OB/GYN Clinical Alert.
Dr. Allen reports no financial relationships relevant to this field of study.
Synopsis: In this large, prospective cohort study, the etonogestrel contraceptive implant was equally effective in normal, overweight, and obese women.
Source: Xu H, et al. Contraceptive failure rates of etonogestrel subdermal implants in overweight and obese women. Obstet Gynecol 2012; Jun 6 [Epub ahead of print].
Through the contraceptive choice project, the authors performed a prospective cohort study in which 9256 women living in the region surrounding St. Louis, Missouri, received a reversible contraceptive method of their choice for up to 3 years at no cost. The participants were read a standardized counseling script which stated that IUDs and the subdermal implant were the most effective methods of contraception. The women then chose their desired method and were followed prospectively for outcomes of contraceptive continuation and pregnancy. Of the first 8445 participants, 1168 (14%) chose the implant and 4200 (50%) chose the IUD (copper IUD or levonorgestrel IUD). The primary outcome was contraceptive failure for either the implant or IUD. Data were stratified according to three categories of body mass index (BMI): normal weight (< 25), overweight (25-29.9), and obese (≤ 30 or greater). Contraceptive-method failure was defined as a pregnancy that occurred when the contraceptive method was actually being used.
Loss to follow-up among the cohort was 6.9%, 12.8%, and 22.5%, at 12, 24, and 36 months, respectively, and did not vary by contraceptive method. Both the IUD and implant group had a similar BMI distribution with about one-third of women in the normal weight, overweight, and obese categories, respectively. Continuation of the implant was 83.3% at 1 year compared to 86.6% for the IUD. There was only one pregnancy among 1377 women-years of implant use, which occurred in an obese woman who had a BMI of 30.7. Therefore, for normal weight, overweight, and obese women using the implant, failure rates were similar at < 1 per 100 women-years. Similarly, among IUD users, there were six pregnancies in normal weight women, six in overweight women, and seven in obese women in the 3 years of follow-up. For the IUD, failure rates were < 1 per 100 women-years in all BMI categories. There was no significant difference between the implant and IUD groups in failure rates for each BMI category.
Commentary
The etonogestrel subdermal implant was approved for use in the United States in 2006 and provides contraception for up to 3 years. The contraceptive efficacy of the implant rivals that of IUDs and sterilization with a 0.05% failure rate.1 The original trials for approval, however, only included women who were normal weight (women > 130% of their ideal body weight were excluded). Therefore, until this study, there were few data on implant effectiveness in overweight and obese women.2
This study alleviates any confusion surrounding implant use in the overweight and obese population. Although we already know that IUDs are unaffected by weight, we can now counsel women that the efficacy of the implant will not be influenced by their weight. In the United States, the unintended pregnancy rate currently stands at 49% and is a major public health problem.3 At the same time, the obesity rate is rising dramatically with 30% of the U.S. population now being considered obese.2 This report will help providers encourage the use of long-acting reversible contraception (LARC) such as IUDs and implants in overweight and obese women. LARC, due to its high efficacy and continuation rates, is considered in the top tier of contraceptive options. The advantages of LARC also include few contraindications and cost-effectiveness.1
Irregular vaginal bleeding, a common side effect of progestin-only contraceptives, is the most frequent reason cited for implant removal. In the clinical trial for approval in the United States, 11% of participants discontinued the implant due to irregular bleeding.4 Counseling women about what to expect prior to implant use is critical to prevent premature discontinuations. On average, women using the implant will have no more bleeding over a 90-day period than they would have had with three menstrual periods. However, the bleeding and spotting are unpredictable and remain that way for the entire 3 years of use. I tell my patients that they will not have regular menstrual periods and to expect episodes of unpredictable bleeding or no bleeding at all. Studies show that in any given 90-day period, 22.2% of women will have amenorrhea, 33.6% will have infrequent bleeding, 6.7% will have frequent bleeding, and 17.7% will have prolonged bleeding.4 I also reassure my patients that the amount of bleeding they may have is not dangerous. There is limited evidence that increased weight does increase bleeding days in women using the implant but more studies need to be done to clarify this issue.4
For women complaining of persistent or prolonged vaginal bleeding, we don't have a proven long-term treatment.5 However, for temporary relief, there is a small amount of anecdotal evidence that oral estrogen alone or in the form of combined oral contraceptives for 1 to 3 months can help some women with this complaint. Another option for treatment is a short course of NSAIDs, such as mefenamic acid 500 mg three times daily for 5 days.5 I think it is worth offering some intervention if it will encourage women to continue with the implant given the benefits of LARC. Despite our best efforts at counseling and treatment of irregular bleeding, some women will ultimately decide to remove the implant. We can counsel them in that case about IUDs if they still desire long-term contraception.
References
- ACOG Committee Opinion no. 450: Increasing use of contraceptive implants and intrauterine devices to reduce unintended pregnancy. Obstet Gynecol2009;114:1434-1438.
- Society of Family Planning, Higginbotham S. Contraceptive considerations in obese women: Release date 1 September 2009, SFP Guideline 2009. Contraception2009;80:583-590.
- Finer LB, Henshaw SK. Disparities in rates of unintended pregnancy in the United States, 1994 and 2001. Perspect Sex Reprod Health 2006;38:90-96.
- Mansour D, et al. The effects of Implanon on menstrual bleeding patterns. Eur J Contracept Reprod Health Care 2008;13(Suppl 1):13-28.
- Mansour D, et al. The management of unacceptable bleeding patterns in etonogestrel-releasing contraceptive implant users. Contraception 2011;83:202-210.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content