In the past 35 years, many types of IUDs have been designed and used clinically. The devices developed and initially used in the 1960s consisted of polyethylene impregnated with barium sulfate to make them radiographic. In the 1970s, to diminish the frequency of the side effects of increased uterine bleeding and pain, smaller plastic devices covered with copper were developed and widely utilized. In the 1980s, devices bearing a larger amount of copper, including sleeves on the horizontal arm (such as in the Cu T 380A and the Cu T 220C), were developed; the multiload Cu 250 and Cu 375 were also introduced during this period. These devices have a longer duration of high effectiveness, and thus need to be reinserted at less frequent intervals than devices carrying a smaller amount of copper. The copper T 380 A IUD is the only copper-bearing IUD currently marketed in the USA, while the multiload Cu 375 is widely used in Europe.

Because of the constant dissolution of copper, even though the amount lost daily is less than that ingested in the normal diet, all copper IUDs must be replaced periodically. The Cu T 380 A is currently approved for use in the USA for 10 years, although it maintains its high level of effectiveness for at least 12 years according to a WHO study. At the scheduled time of removal, the device can be removed and another inserted during the same office visit.

Adding a reservoir of levonorgestrel to the vertical arm also increases the effectiveness of the T-shaped devices. The currently marketed LNG-IUS realeses 20 μg of levonorgestrel into the endometrial cavity each day. This amount is sufficient to prevent pregnancy by keeping the cervical mucus thick and viscid, preventing sperm transport into the endometrial cavity and oviducts. Serum levonorgestrel levels are lower than occur with levonorgestrel implants or oral contraceptives. Because of the progestational effect upon the endometrium, the amount of uterine bleeding is reduced to about 5 mL per cycle and this device has been used to treat heavy menstrual bleeding. The LNG-IUS needs to be replaced after 5 years of use, as the reservoir of levonorgestrel becomes depleted after this time. The surface area of plastic in this small device is insufficient to produce a sufficiently large leukocytic response to yield a high level of contraceptive effectiveness without levonorgestrel. This device is extremely effective, with a 5-year cumulative pregnancy rate of 1.1 per 100 women.

The main mechanism of contraceptive action of copper-bearing IUDs in humans involves a spermicidal effect. The presence of the foreign body in the uterine cavity generates a local sterile inflammatory reaction. In addition to causing phagocytosis of spermatozoa, tissue breakdown products of these leukocytes are toxic to all cells, including spermatozoa and the blastocyst. The amount of inflammatory reaction, and thus contraceptive effectiveness, is directly related to the size of the intrauterine foreign body. Copper markedly increases the extent of the inflammatory reaction, which explains why this metal has been added to the small frame of T-shaped devices. In addition, copper impedes sperm transport and viability in the cervical mucus. Because of the spermicidal action of IUDs, very few, if any, sperm reach the oviducts, and the ovum usually does not become fertilized.

The LNG-IUS prevents sperm transport through the thickened cervical mucus, so the ovum is not fertilized. The LNG-IUS, like the copper device, has a very low ectopic pregnancy rate, providing additional evidence that fertilization does not usually occur with both these devices.

Upon removal of the IUD, the inflammatory reaction rapidly disappears. Resumption of fertility following all types of IUD removal is prompt and occurs at the same rate as resumption of fertility following discontinuation of the barrier methods of contraception. The incidence of term deliveries, spontaneous abortion, and ectopic pregnancies in conceptions occurring after IUD removal is the same as in women who do not use any contraception.

Although it is widely believed that the optimal time for insertion of an IUD is during the menses, data indicate that the IUD can be safely inserted on any day of the cycle as long as the woman is not pregnant. Because IUD insertion introduces bacteria into the endometrial cavity, it is preferable to insert it after the menses cease, to avoid providing a good environment for bacterial growth. IUDs can be safely inserted at the time of the routine postpartum visit after a term delivery when the uterus is involuted, whether or not the woman is nursing her infant. IUDs may also be inserted immediately after completion of a spontaneous or induced abortion.

Incidence

In the first year of use with both types of IUD, there is less than a 1% pregnancy rate, a 10% expulsion rate, and a 15% rate of removal for medical reasons (mainly bleeding and/or pain). The incidence of each of these events diminishes steadily in subsequent years.

A WHO study of the Cu T 380A found that termination rates for adverse effects continued to decline annually following the first year after insertion for the following 12 years. In this study, the cumulative percentage discontinuation rates for reasons of pregnancy, bleeding and pain and expulsion at the end of 12 years were 1.7%, 35.3% and 12.5%. A large study of the LNG-IUS reported that cumulative termination rates for pregnancy, bleeding and pain and expulsion were 0.5%, 13.8% and 5.8% per 100 women respectively after 5 years.

Uterine bleeding

The majority of women discontinuing this method of contraception do so for medical reasons. Nearly all medical reasons accounting for removal of copper-bearing IUDs involve one or more types of abnormal bleeding, either heavy and/or prolonged menses or intermenstrual bleeding. The amount of blood lost in each menstrual cycle is significantly greater in women using copper-bearing IUDs than in nonusers. In a normal menstrual cycle, the mean amount of menstrual blood loss (MBL) is approximately 35 mL. The copper T 380 A IUD is associated with a 55% increase in MBL. In contrast, with the levonorgestrel-releasing IUD, the amount of blood loss is significantly reduced, declining to approximately 5 mL per cycle after 6 months of use.

In a study of women using the copper T 380, no significant change arose in mean measurements of several hematologic parameters, including hemoglobin, hematocrit, and erythrocyte count, when they were taken 3, 6, and 12 months after IUD insertion when compared with mean values before insertion. No significant change in mean serum ferritin levels was found at 3, 6 and 12 months after IUD insertion.

Excessive bleeding in the first few months following IUD insertion should be treated with reassurance and supplemental oral iron, as well as systemic administration of a prostaglandin synthetase inhibitor during menses. The bleeding usually diminishes with time, as the uterus adjusts to the presence of the foreign body. Irregular and frequent bleeding usually occurs in the first few months after insertion of the LNG-IUS. After this time bleeding is usually scant and about 20% of users are amenorrheic 1 year after insertion of the device.