Intrauterine device
The intrauterine device, also known as an intrauterine contraceptive device, is a small, T-shaped birth control device that is inserted into the uterus to prevent pregnancy. IUDs are a form of long-acting reversible contraception.
IUDs are a safe and effective birth control method that can be divided into two major categories based on the mechanism the device uses to prevent pregnancy: hormonal IUDs and copper IUDs. Both types of IUDs can be used in most women, including adolescents, those who have never been pregnant, and those who have previously had children. They do not affect breastfeeding and can be inserted immediately after delivery. They may also be used immediately after an abortion. Globally, 19.4% of women of reproductive age use intrauterine contraception according to 2019 data. The IUD has a more invasive insertion procedure than other birth control methods. However, among birth control methods, IUDs, along with other contraceptive implants, result in the greatest satisfaction among users.
Both hormonal and copper IUDs have failure rates of <1%, meaning less than 1 in 100 individuals with an IUD have an unintended pregnancy. In comparison, combined hormonal contraception methods have a failure rate of about 2% with perfect use and 4-7% with typical use. Barrier methods, such as the male condom, have a failure rate of approximately 13% and fertility awareness methods, have a failure rate of 22%. Once an IUD is removed, even after long-term use, fertility returns to normal rapidly.
Hormonal IUDs often reduce menstrual bleeding by up to 90% or stop menstruation altogether. Users may experience daily spotting following insertion, and it can take up to six months to see a decrease in bleeding. Copper IUDs are preferred by some as a non-hormonal birth control option, but they can increase the amount and duration of menstrual bleeding by approximately 50% and lead to worsening of menstrual cramps. More serious potential complications of both types of IUD include expulsion and perforation of the uterus.
IUDs can also be used as emergency contraception for the prevention of pregnancy immediately following unprotected sex. Copper IUDs are considered the most effective form of emergency contraception, with only 0.1% of those with a copper IUD placed within 5 days of unprotected sex becoming pregnant. Hormonal IUDs are also an acceptable method for emergency contraception, however there is less data regarding effectiveness.
History
The first IUD was developed in 1909 by the German physician Richard Richter of Waldenburg. Unlike modern intrauterine devices, early interuterine devices crossed both the vagina and the uterus, causing a high rate of pelvic inflammatory disease.Ernst Gräfenberg, another German physician, created the first Ring IUD, Gräfenberg's ring, made of silver filaments. His work was suppressed during the Nazi regime, when contraception was considered a threat to Aryan women. He moved to the United States, where his colleagues H. Hall and M. Stone took up his work after his death and created the stainless steel Hall-Stone Ring.
Jack Lippes helped begin the increase of IUD use in the United States in the late 1950s. In this time, thermoplastics, which can bend for insertion and retain their original shape, became the material used for first-generation IUDs. Lippes also devised the addition of the nylon string to facilitate IUD removal. His trapezoid-shaped Lippes Loop IUD became one of the most popular first-generation IUDs. In the following years, many different-shaped plastic IUDs were invented and marketed. One of these first-generation IUDs was the Dalkon Shield, whose poor design caused bacterial infection and led to thousands of lawsuits. Although it was removed from the market, the Dalkon Shield had a lasting, negative impact on IUD use and reputation in the United States.
The invention of the copper IUD in the 1960s introduced the capital T-shaped design used by most modern IUDs. U.S. physician Howard Tatum determined this shape would work better with the space of the uterine cavity. He predicted this would reduce rates of IUD expulsion. Further, Tatum and Chilean physician Jaime Zipper discovered that copper could be an effective spermicide and developed the first copper IUD. Improvements by Tatum led to the creation of the TCu380A, which is currently the preferred copper IUD.
The hormonal IUD was also invented in the 1960s and 1970s with the goal of mitigating the increased menstrual bleeding associated with copper and inert IUDs. The first model, Progestasert, lasted for one year of use and was quickly discontinued. The Mirena hormonal IUD was released in 1976.
China
In China, the use of IUDs by state health services was part of the government's efforts to limit birth rates. From 1980 to 2014, 324million women were inserted with IUDs, in addition to the 107million who had tubal ligation. Until the mid-1990s, the state-preferred IUD was a stainless steel ring, which had a higher rate of complications compared to other types of IUD. It gave rise to the idiom p=shànghuán, meaning "insert a loop". Nowadays, the IUDs include T and V shapes, the former being the most common and easiest to remove.Mechanism
The main mechanisms of action of IUDs occur before fertilization, by preventing sperm from ever reaching the egg. The specific mechanism for preventing sperm from reaching the egg differs by type of IUD.Hormonal
Hormonal IUDs work by releasing a small amount of levonorgestrel, a progestin. The progestin released by hormonal IUDs primarily acts locally within the uterus, resulting in much lower systemic progestin levels than other progestogen only contraceptives. Each type of hormonal IUD varies in size, amount of levonorgestrel released, and duration of effectiveness. The predominant mechanism of action of progestin in the uterus is thickening the cervical mucus to prevent sperm from reaching the fallopian tubes, and ultimately the egg. Hormonal IUDs can also thin the endometrial lining and potentially impair implantation, but this is not their usual function. Because they thin the endometrial lining, hormonal IUDs often reduce or entirely stop menstrual bleeding. As a result, they are often used to treat menorrhagia, once pathologic causes of menorrhagia have been ruled out.Non-hormonal
Copper
Copper IUDs acts as a spermicide. Copper ions released from the IUD damage sperm and disrupt their ability to move, preventing sperm from traveling through the cervical mucus or destroying them as they pass through so that they never meet the egg. They also start a local inflammatory reaction that causes the uterus and fallopian tubes to produce a fluid that contains white blood cells, enzymes, and prostaglandins, which are toxic to sperm.While not the main mechanism of action, studies have found that copper can also alter the endometrial lining. This alteration can prevent implantation of a fertilized egg, but it cannot disrupt a fertilized egg that has already been implanted in the uterine lining.
Inert
Inert IUDs are not approved for use in the United States, UK, or Canada. Inert IUDs do not have a bioactive component. They are made of inactive materials like stainless steel or plastic. Their primary mechanism of action is causing a local foreign body reaction, which makes the uterine environment hostile both to sperm and to implantation of an embryo. They may have higher rates of preventing pregnancy after fertilization, instead of before fertilization, compared to copper or hormonal IUDs.Types
The types of intrauterine devices available, and the names they go by, differ by location. The WHO ATC labels both copper and hormonal devices as IUDs. In the United Kingdom, there are more than 10 different types of copper IUDs available. In the United Kingdom, the term IUD refers only to these copper devices. Hormonal intrauterine contraception is labeled with the term intrauterine system.In the United States, there are two types available:
In China, where IUDs are the most common form of contraception, copper IUD production replaced inert IUD production in 1993. However, as of 2008, the most common IUD used by immigrants presenting to Canadian clinics for removal of IUDs placed in China was still the stainless-steel ring. Because the SSR has no string for removal, it can present a challenge to healthcare providers unfamiliar with IUD types not available in their region.
Insertion and removal
IUD insertion can occur at multiple timepoints:- interval insertion, the most common, occurs in separation from any recent pregnancy;
- post-abortion or post-miscarriage insertion, occurs following an abortion or miscarriage when the uterus is known to be empty;
- postpartum insertion, occurs after a woman gives birth either immediately, while the woman is still in the hospital, or delayed, up to 6 weeks following delivery. Insertion timing changes the risk of IUD expulsion.