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If the period-like cramps mean I am ovulating, is my Implanon implant no longer effective? #202/12

Hi, I'm a little worried. I've got the Implanon implant in now and it's due to be changed in April.  However, for the last 2-3 months, I've noticed halfway through my cycle I have started getting period-like cramps. I have never had these before and have been told this could be ovulating pains. Isn't the Implanon supposed to stop ovulation? And if I've started ovulating, does that mean my Implanon is no longer working? Can the Implanon just stop working before the 3 years are up?


Any feedback would be greatly appreciated.


Thank you.

A:        Good for you…I have good news!


While no method is 100%, Implanon is extremely effective for the entire 3 years.  In fact, no pregnancies have been reported in the three published articles of 270 women who used Implanon for a 4th year.


Ovulation return may happen, but Implanon is working through effects on cervical mucus and on the lining of the uterus.

The following information is from the new 20th edition of Contraceptive Technology, chapter 8 by Dr. Elizabeth Raymond:



Implants are among the most effective of the available contraceptive methods; they are in the top tier of effectiveness. (See Figure 3-1 in Chapter 3 on Choosing a Contraceptive.) From a clinical viewpoint, their efficacy is indistinguishable from that of sterilization and intrauterine devises. To date, no pregnancies have been observed in prospective or retrospective cohort studies of Implanon, which included a total of more than 4,500 women and more than 7,000 women-years of exposure. However, pregnancies in Implanon users have been reported to regulatory authorities and Merck, and in case reports in the medical literature. Of 173 classifiable Implanon failures reported to the Therapeutic Goods Administration in Australia, 49% were attributed to non-insertion of the implant, 27% were apparently conceived before the women had Implanon inserted, 11% were ascribed to insertion outside the recommended time in the menstrual cycle, 2% occurred after expulsion of the implant, and 12% were true product failures. In a much larger number of classifiable pregnancies reported to Merck (which may have included most of the Australian pregnancies), half had no implant present, and 38% were true product failures. In both series, a quarter to a third of the true method failures occurred in women taking possibly interacting drugs. Based on Implanon sales data, authors have estimated an approximate failure of 0.5 to 1 pregnancy/1,000 Implanon insertions.


            Whether user characteristics, such as body weight, might reduce the efficacy of Implanon is unknown. Serum etonorgestrel levels appear inversely related to body weight, although no evidence has been found of a relationship between weight and ovulation or pregnancy rates. The number of obese women included in prospective and retrospective studies was relatively small.


            Implanon is marketed with a duration of action of 3 years. However, pharmacokinetic data from Implanon users show stable serum concentrations of etonorgestrel out of 36 months, suggesting that the method is effective from longer than that. (See Figure 8-1). Three studies in which a total of 275 women used Implanon for longer than 3 years found no pregnancies during the fourth year of use.


To learn more about the advantages and disadvantages of the copper T (ParaGard) IUD, go to our website: www.managingcontraception.com and click on
Choices.  You can also order this wonderful new educational book from our website or by calling 404-875-5001.  Do you have your copy yet?

Key Words:   Implanon implant, changed, cycle, period-like cramps, ovulating pains, effective, pregnancies, studies, cervical mucus, lining, uterus

Posted 2-8-2012, Updated 2-29-2012


Robert A. Hatcher MD, MPH
Emeritus Professor of Gynecology and Obstetrics
Emory University School of Medicine
Atlanta, GA

The directors and owners of this website and any publications and information concerning health matters offered here advise a person with a particular problem to consult a primary-care clinician or a specialist in obstetrics, gynecology, or urology (depending on the problem or the contraceptive) as well as the product package insert and other references before diagnosing, managing, or treating the problem.
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