SANTA FE, N.M. — IUDs, once considered an unsafe method of birth control, appear to be making a comeback.
Recent data from the Centers for Disease Control and Prevention suggest that about 5.5% of women aged 15-44 years use IUDs for contraception, which is equivalent to those who choose natural family planning as their primary form of birth control (Vital Health Stat. 2010;23:1-44). That's up significantly from 1995, when fewer than 1% women used IUDs.
“IUDs that we currently have available in the United States are safe,” Dr. Sarah W. Prager said at the meeting. “They're highly efficacious and they're still vastly underused in the United States. It would behoove us, for our patients' sake, to get beyond some of our biases based on our past negative associations.”
In her opinion, the downfall of IUDs emerged soon after the Dalkon Shield was introduced in 1971. Insertion of that device was associated with septic abortion and death, and it caused a fivefold increased risk of pelvic inflammatory disease (PID), compared with other IUDs from that time period, said Dr. Prager of the University of Washington, Seattle. Hypothesized reasons for the problems included the braided polyfilament strings and the fact that a smaller Dalkon Shield was marketed specifically to nulliparous women.
“There is no question that nulliparous women are less likely to be married and therefore more likely to have more partners, which puts them at an increased risk for a sexually transmitted infection,” Dr. Prager said. “Another hypothesis is that the increased surface area of the shield made it more able to drag bacteria from the vagina into the uterus. Also, it was not very effective, with a 2% failure rate per year.”
Of the estimated 6 million pregnancies annually in the United States, almost half are unintended, she said. Of those unintended pregnancies, slightly more than half occur in women who are using some form of contraception. “The pill is still the most commonly used method of reversible contraception, followed by condoms, followed by nothing, followed by [intrauterine contraception].”
Family planning clinicians are increasingly recommending IUDs, she added, because the two devices that are currently available in the United States – the copper T 380A (Teva Women's Health Inc.'s ParaGard) and the LNG IUS (levonorgestrel intrauterine system, marketed as Mirena by Bayer Healthcare Pharmaceuticals) – are just as effective in preventing pregnancy as is female sterilization. “So effectively, you have reversible sterilization with these products, which is amazing for women who want more long-term prevention of pregnancy,” Dr. Prager said, noting the products' 0.5% failure rate over 5 years.
She credits the pendulum shift in part to mechanical improvements in contemporary IUDs, compared with those from years gone by. For example, plastic IUDs from yesteryear “were less effective in preventing pregnancy. They would depend on surface area for their function and they would cause sterile inflammation based on mass effect.”
ParaGard, on the other hand, is made of copper, which decreases the motility and viability of sperm. “It also disrupts oocyte division and sterilization,” she said. “Secondarily, it inhibits implantation.” It is approved for 10 years of use.
Mirena inhibits fertilization primarily by thickening cervical mucus. It also inhibits sperm motility and function, suppresses the endometrium, causes a weak foreign body reaction, and inhibits ovulation cycles in about 10% of women. It is approved for 5 years of use.
Another factor in the widening acceptance of IUDs, Dr. Prager said, is that there were biases in many studies linking infection and infertility risk to the use of devices that were being used in the 1970s, when about 10% of women used IUDs. “Inappropriate comparison groups were sometimes used,” she said. “Women using contraceptives that lower the risk of PIDs' is probably not an appropriate comparison group. Systematic overdiagnosis of PID in IUD users is also a possibility in a lot of these studies, because [that] was a concern after the early 1970s. Another reason is the inability to control for a number of confounders, such as number of sexual partners.”
Disclosures: Dr. Prager disclosed that she is an Implanon speaker/trainer for Schering-Plough. She has also received salary support from a grant partially subsidized by Ortho-McNeil Pharmaceuticals.