Intrauterine devices (IUDs) are a highly effective and long-lasting form of reversible contraception, offering over 99% efficacy in preventing pregnancy. A common concern for those considering this option involves the device’s relationship with ovarian cysts. Whether an IUD causes these fluid-filled sacs is complex, as the answer depends heavily on the type of IUD used and its specific mechanism of action. This article examines how different IUDs interact with the ovarian cycle and the resulting risk of cyst formation.
Understanding Ovarian Cysts
An ovarian cyst is a fluid-filled sac that develops on or within an ovary. They are a common occurrence in people with regular menstrual cycles. The majority are known as functional cysts, which are a normal result of the monthly reproductive process. Functional cysts are broadly categorized into follicular cysts and corpus luteum cysts.
During a typical cycle, a follicle—a small sac containing an egg—grows on the ovary. If this follicle fails to rupture and release the egg, it can continue to grow and retain its fluid, forming a follicular cyst. A corpus luteum cyst forms after the egg is released, when the empty follicle seals up and collects fluid, sometimes with a small amount of blood. These functional cysts are almost always benign, often cause no symptoms, and typically resolve on their own within one to three months.
Hormonal IUDs and Functional Cyst Formation
Hormonal IUDs (e.g., Mirena, Liletta, Skyla, and Kyleena) release a small, localized dose of the progestin hormone levonorgestrel into the uterus. This progestin works primarily by thickening cervical mucus and thinning the uterine lining to prevent pregnancy. Unlike combination birth control pills, these IUDs do not consistently suppress ovulation, which is where the effect on cyst formation originates.
The localized, low-dose progestin can cause subtle disturbances in the ovarian function and disrupt the typical follicular development and rupture process. This interference results in a slightly higher incidence of follicular cysts that persist longer than they normally would. Studies show that the risk of developing a benign ovarian cyst in the first year of use can be around 7.5% for higher-dose hormonal IUDs, compared to a lower baseline rate in non-hormonal users.
These cysts are generally considered a minor side effect because they are functional, transient, and clinically insignificant. Research indicates that 80% to 90% of these cysts in hormonal IUD users resolve spontaneously, often within three months. They are not associated with an increased risk of pathological or dangerous ovarian cysts. The IUD’s action may temporarily increase the occurrence of these benign sacs, but it does not increase the risk of developing complex or cancerous cysts.
Non-Hormonal IUDs and Cyst Risk
The copper IUD (ParaGard) operates through a fundamentally different, non-hormonal mechanism. This device works by creating a localized inflammatory reaction in the uterus, which produces an environment hostile to sperm and prevents fertilization. Because the copper IUD does not release hormones, it does not interfere with the body’s natural ovulatory cycle.
The ovary continues its normal function, releasing an egg each month, and hormonal fluctuations remain largely unchanged. Consequently, the copper IUD does not increase the risk of functional ovarian cysts above the baseline risk experienced by those not using hormonal contraception. The rate of cyst formation in copper IUD users is comparable to those with spontaneous menstrual cycles, contrasting with the effect seen with progestin-releasing systems.
Symptoms and When to Seek Medical Guidance
The majority of functional ovarian cysts, including those that may form while using a hormonal IUD, are asymptomatic and go unnoticed. When symptoms occur, they are typically mild and may include a dull ache or pressure in the pelvis or lower abdomen, or bloating. These mild symptoms often resolve as the cyst shrinks on its own.
While rare, a cyst can cause complications requiring immediate medical attention, such as rupture or ovarian torsion (twisting of the ovary). Warning signs that necessitate urgent medical guidance include sudden, severe pelvic pain, especially if accompanied by nausea, vomiting, or fever. Any instance of new, persistent, or worsening pelvic discomfort should be discussed with a healthcare provider to ensure proper diagnosis and management. Regular check-ups are recommended to monitor overall reproductive health.