Dr. Gariepy reports no financial relationships relevant to this article. Dr. Creinin reports that he is a consultant to, and a speaker for, Schering-Plough.
Progestin-only contraception—a diverse group of oral (progestin-only pills, or so-called minipills), injectable (depot medroxyprogesterone acetate), intrauterine (the levonorgestrel intrauterine system), and implantable (etonogestrel implant) methods—may offer advantages over estrogen-containing contraception:
- the flexibility of distinctive methods of delivery
- the ability to initiate the method in postpartum breastfeeding women
- enhanced safety in women who should not be exposed to exogenous estrogens.
Unpredictable bleeding is a major disadvantage of progestin-only contraception, however, and can cause women to discontinue these methods—and discontinuation without an effective backup method creates a high risk of unplanned pregnancy. The significant variability in bleeding patterns among progestin-only contraceptive methods hinders our ability to counsel patients about them.
Furthermore, the lack of uniform definitions of bleeding patterns with hormonal contraception, including progestin-only methods, makes it difficult to counsel women accurately and compare bleeding patterns among methods.
Accurate prediction of the bleeding patterns associated with progestin-only contraception could lower the discontinuation rate. For example, studies have shown that pretreatment counseling about expected side effects increases approximately fourfold the acceptability and continuation of depot medroxyprogesterone acetate.1,2
In this Update, we review the data on bleeding patterns associated with progestin-only contraceptives, including the likelihood of 1) amenorrhea and 2) discontinuation due to changes in the bleeding pattern.
We also discuss what has been learned about the treatment of changes in bleeding patterns induced by progestin-only contraception.
Our goal? To summarize the findings in a comprehensive way that makes it easier for you to discuss expected bleeding patterns with your patients—so that women can choose the method of contraception that is the best fit for them.
Describing bleeding patterns is a challenging task
One of the difficulties of interpreting clinical data on bleeding patterns—with any type of contraception—is the lack of a universally accepted standard for collecting and reporting these data. The first suggestions for standardization were made in 1976, when Rodriguez and colleagues proposed using 90-day reference periods for analysis, as a way to minimize variability among individual menstrual cycles.3
Subsequently, the World Health Organization’s (WHO’s) Special Programme of Research, Development and Research Training in Human Reproduction developed recommendations for data collection, terminology, presentation, and data analysis when reporting vaginal bleeding during clinical trials of hormonal contraception. These recommendations became known as the WHO Belsey criteria (TABLE 1). They remain the standard.4
Under the WHO Belsey system:
- vaginal blood loss for which a woman uses sanitary protection is classified as bleeding
- vaginal blood loss that does not result in the use of sanitary protection is considered spotting.
This system also specifies indices for evaluating the bleeding pattern for each woman and reference period, including the number of bleeding-spotting days, number of bleeding-spotting episodes, lengths of bleeding-spotting episodes, and bleeding-spotting-free intervals. A bleeding-spotting episode is defined as one or more consecutive days during which blood loss (bleeding or spotting) has been recorded, each episode being bounded by bleeding-spotting-free days. The WHO Belsey criteria also identified subgroups that have “clinically important bleeding patterns” (TABLE 1).
But not all researchers use the WHO Belsey criteria. Many trials use, and report, their own system of analysis. Some researchers have chosen reference periods of other durations and study periods that range from 1 to 5 years. Some studies report bleeding patterns by number of days, and others report the percentage of women experiencing a given bleeding pattern during a reference period. The lack of uniformity results in data that are difficult to compare from one study to the next—and to explain to our patients.
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It’s unclear whether any of our research definitions of clinically significant bleeding have ever been validated as clinically important to our patients. Multiple studies do show that changes in menstrual bleeding patterns are a significant cause of dissatisfaction with any given contraceptive method, but we don’t know if the number of days of bleeding-spotting or the predictability of this bleeding-spotting is the critical piece of information we should be relating to our patients.