An intrauterine device (IUD) is a small, T-shaped piece of flexible plastic that a healthcare provider places inside the uterus. IUDs provide long-acting reversible contraception (LARC) and are highly effective, offering greater than 99% efficacy in preventing pregnancy. One or two thin, plastic retrieval strings extend from the base of the device, passing through the cervix and hanging into the upper vagina. The color of these strings, which are primarily designed for clinical use, can help identify the specific type of IUD.
The IUD Identified by Blue Strings
The device most commonly associated with blue removal strings is the Kyleena IUD, a hormonal device manufactured by Bayer. Kyleena uses a lower dosage of the progestin hormone levonorgestrel compared to other hormonal options. The blue threads are attached to the device’s vertical stem, which also contains a silver ring that makes the IUD visible on an ultrasound. Kyleena is approved for pregnancy prevention for up to five years, and its smaller size may influence patient selection.
Another hormonal device, Liletta, also uses blue threads for removal. Liletta contains a higher dose of levonorgestrel (52 milligrams) and is approved for use for up to eight years. Since two different manufacturers use blue threads, color coding is not exclusive to a single brand. Healthcare providers confirm the IUD type by checking the patient’s medical records and the device’s unique characteristics.
Why IUDs Have Retrieval Strings
Retrieval strings serve the dual purpose of device confirmation and removal. Following insertion, the strings allow a healthcare provider to confirm during follow-up examinations that the IUD remains correctly positioned within the uterine cavity. The provider visually checks that the strings are visible extending from the cervical opening.
The strings also serve as the mechanism for the device’s removal when its lifespan is over or when the patient wishes to discontinue use. During removal, the clinician gently grasps the strings and pulls with steady traction. This action collapses the IUD’s T-shape, allowing it to be easily withdrawn through the cervix. Color coding is an efficient way for clinicians to immediately identify the IUD type, distinguishing between hormonal and non-hormonal devices at a glance.
Color Coding for Other Popular IUD Brands
Most other popular IUDs use different colored strings for identification. For instance, the copper IUD, Paragard, uses white threads. Paragard is the only non-hormonal option available in the United States and provides effective contraception for up to ten years. This device works by triggering a localized inflammatory reaction to the copper, which is toxic to sperm and prevents fertilization.
Many hormonal IUDs, such as Mirena and Skyla, typically use silver threads. These devices release varying doses of the progestin levonorgestrel, which thickens cervical mucus and thins the uterine lining. Mirena is approved for up to eight years of use, while Skyla is approved for up to three years. Different thread colors act as a quick visual marker for healthcare professionals to differentiate the specific device and its mechanism.
Patient Steps for String Monitoring
Patients with an IUD are advised to perform regular checks of their retrieval strings to ensure the device has not moved. The best time for self-monitoring is usually after the end of the menstrual cycle when the cervix is slightly lower and softer. The patient gently inserts a clean finger into the vagina and feels for the two thin strings emerging from the cervix. The strings should feel roughly the same length as they did after the initial check-up.
Contact a healthcare provider immediately if the strings feel significantly shorter or longer than usual, or if the hard plastic body of the IUD is felt. A change in string length may indicate that the IUD has shifted or is partially expelled, which could compromise its effectiveness. Any concerns should prompt a clinical evaluation with a medical professional.