Intrauterine Device (IUD)
An intrauterine device (IUD) is a small, T-shaped device inserted into the uterine cavity for contraception. Two primary types are in clinical use.
The copper IUD works without hormones. Copper ions impair sperm motility and reduce fertilization. At higher concentrations, copper may also affect implantation if fertilization occurs, though the primary mechanism operates before fertilization.
The hormonal IUD releases levonorgestrel, a synthetic progestin, locally into the uterine cavity. It thickens cervical mucus, thins the endometrial lining, and may suppress ovulation in some users, particularly in the first year. Its primary mechanisms are cervical and endometrial. Whether post-fertilization effects occur remains a matter of scientific debate and is directly relevant to informed consent for couples who consider fertilization the beginning of a new life.1
Side effects: the copper IUD frequently causes heavier menstrual bleeding and increased cramping. The hormonal IUD frequently causes irregular bleeding or amenorrhea. Amenorrhea eliminates menstrual cycle data as a diagnostic source. Both types carry a small risk of expulsion, uterine perforation at insertion, and infection during the insertion procedure.
RRM does not prescribe or recommend IUDs. Understanding how they work is part of informed care.
Cited in this entry
- Stanford JB, Mikolajczyk RT. Mechanisms of action of intrauterine devices: update and estimation of postfertilization effects. Am J Obstet Gynecol. 2002. https://rrmacademy.org/library/mechanisms-of-action-of-intrauterine-devices-update-and-estimation-of-postfertil-reczn2vz80mt5hrwl/
This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.