A. Intrauterine devices (IUDs) have been around for over 80 years, in humans. In fact, there is a legend that caravan drivers used to use intrauterine stones to prevent pregnancies in their camels during long crossings of the desert! But despite our long history with IUDs, some controversy about how it works still exists.
The IUD is one of the most efficacious forms of reversible contraception available today with a failure rate of less than 1%. Often, the IUD is a T-shaped device which is inserted into the woman's uterus in the doctors office (takes about 15 minutes start to finish). The IUDs today are of 1 of 2 sorts, copper coated or with a progesterone (a hormone) reservoire.
Originally, most people believed that IUDs worked by causing an ongoing
irritation of the lining of the uterus (the endometrium), simply by
virtue of it being there. This irritation would make it difficult for any
fertilized egg to implant in the uterus. So yes, it was believed to be an
abortifacient. Newer studies, however, have shown that the copper
IUD actually impedes both the sperm and the egg's mobility, thereby
preventing fertilization in the first place. This doesn't appear to be the
case with the progesterone IUDs, however. The progesterone IUDs appear to
work less by irritative effects as by the changes in the lining of the uterus
caused by the hormone. Progesterone will cause the endometrium to have fewer
blood vessels supplying it, thin it out and thereby make it less available
for a fertilized egg to implant in it.
The IUD has a long and often "rocky" history. IUDs reached their peak in popularity in the 1960s, when a woman could choose from literally dozens of shapes and brands, with or without medication on them (the "Lippes Loop", the "Birnberg Bow", etc). In the 1970's however, the Dalkon Shield, the most popular of all IUDs at the time, was shown to be dangerous and removed from the market. The company's ensuing bankrupcy, multiple lawsuits and a lot of negative media attention led to a dramatic decline in the use of IUDs from which we are only slowly beginning to emerge.
IUDs are not for everyone. A talk with your family doc about the benefits and the risks of the IUD, your own particular medical history, and your contraceptive needs is the best way to decide what's best for you.
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