Globally, 14 percent of reproductive-aged women use intrauterine contraception, and in the United States, 10 percent of contracepting women use this method (Buhling, 2014; Daniels, 2015). he five intrauterine devices (IUDs) currently approved for use in the United States are chemicaly active and continually elute either copper or levonorgestrel. These all have arT-shaped frame of polyethylene that is compounded with barium to render them radiopaque. Of devices, Mirena and Liletta both measure 32 X 32 mm and contain a 52-mg levonorgestrel-releasing cylinder reservoir in the stem of the T (Fig. 38-1). Two trailing strings that are tan (Mirena) or blue (Liletta) are attached to the distal stem to aid eventual device removal. Skyla-known asJaydess in some countries-contains 13.5 mg of levonorgestrel. It has smaller dimensions-28 X 30 mm-and was sized to more appropriately it a nulliparous uterus (Gemzell-Danielsson, 2012). yleena has the same dimensions but contains 19.5 mg of the same progestin. Two trailing strings of Skyla are tan, and those of yleena are blue. Skyla and yleena can be diferentiated from Mirena and
Liletta visually and sonographically by a silver ring near the junction of their stem and arms. Mirena and yleena are cur rently approved for 5 years of use following insertion, whereas
Skyla and Liletta are approved for 3 years.
he third device, the T380A IUD named ParaGar, is wound with copper, and two strings extend from the stem base. Originally blue, the strings are now white. It is currently approved for 10 years of use following insertion (T eva Wom en's Health, 2014).
In addition to these ive currently marketed IUDs, women may retain discontinued brands. A Lippes Loop has two "S" shapes stacked one on the other. he Dalkon Shield has a crab form, whereas a Copper 1 mirrors that number. Progestasert is an early T -shaped progestin-releasing IUD. Last, various metaleluting ring devices are common in Asia.
All these IUDs are efective. Failure rates are well below 1 percent and similar overall to those of tubal sterilization (Thonneau, 2008; Trussell, 2011 b). heir mechanisms have not been precisely deined, but prevention of fertilization is now favored.
With the LNG-IUS, long-term progestin release leads to endometrial atrophy, which hinders normal implantation (Silverberg, 1986). Moreover, progestins create scant viscous cervical mucus that obstructs sperm motility (Apter, 2014; Moraes, 2016). Within the uterus, an intense local endometrial inlammatory response is induced, especially by coppercontaining devices. Cellular and humoral components of this inlammation are expressed in endometrial tissue and in luid illing the uterine cavity and fallopian tubes. These lead to decreased sperm and egg viability (Ortiz, 2007). Also, in the unlikely event that fertilization does occur, the same inlammatory actions are directed against the blastocyst. Also, with the Cu-IUD speciically, copper levels rise in the cervical mucus of users and act to decrease sperm motility and viability (Jecht, 1973). he above efects are considered primary for contraception because ovulation inhibition is inconsistent with the LNG-IUS and lacking with the Cu-IUD (Nilsson, 1984).