how does an IUD work

Birth control is crucial in preventing unintended pregnancies. While the term ‘birth control’ is often associated with oral birth control methods such as ‘The Pill’, the most effective form of birth control is an intrauterine device (IUD), which works to prevent fertilization of the egg. They are also the most cost-effective birth control method despite the higher upfront cost. Approximately 150 million women worldwide use an IUD as a form of birth control, although many are still misinformed about IUDs as a viable birth control option.

What is an IUD?

An IUD is a long acting reversible contraception (LARC), meaning that while its effects are long-term, they will reverse immediately after the IUD is removed, restoring fertility. IUDs are T-shaped and inserted into the uterus by a healthcare professional with the top ends of the device positioned by the entrance of each fallopian tube – the location where eggs are released and fertilized. There are different sizes available, ranging from 28mm-32mm wide and 30mm-36mm long. The range in size is advantageous for adolescents and women who have never vaginally delivered a child since they often have narrower uterine widths, which require smaller devices.

How does an IUD work?

There are two types of IUDs approved for use in the US and Canada: copper-containing IUD and levonorgestrel (LNg)-containing IUD. Both types of IUDs are equally effective, with the copper IUD and LNg IUD having a .08% and .02% failure rate respectively; however, the way in which they prevent pregnancies differ.

The LNg IUD releases progestin – a synthetic form of the female reproductive hormone progesterone – to suppress the growth of the endometrium (the lining of the uterus), which is necessary for the proper development of a fertilized egg. Progestin released by the IUD also desensitizes the endometrium to the female reproductive hormone estradiol, which inhibits ovulation. It also thickens the cervical mucous, which makes it more difficult for sperm to travel into the uterus. This hormonal IUD comes in three different doses, 13.5mg, 19.5mg, and 52mg, with the smallest dose lasting three years and the two latter doses lasting five years. All three strengths have been proven to be equally effective at preventing unintended pregnancies. LNg IUDs often result in lighter or full cessation of regular menstrual bleeding due to progestin’s suppression of endometrium growth. Lastly, LNg IUDs require careful planning for an insertion appointment date as one must have it inserted within seven days of the beginning of their menstrual bleeding for it to be effective immediately. If this is not possible, it is recommended that an individual use another form of birth control for seven days after the insertion date.

The other type of IUD, the copper-containing IUD, works by releasing small amounts of copper ions, which act to impair sperm, rendering them unable to reach the egg or successfully fertilize it. Due to its ability to prevent the fertilization of an egg that has been released, reports indicate that if a copper IUD is placed within five days of unprotected sex it can act as an emergency contraceptive. The copper IUD has a longer effectiveness period than the LNg IUD, needing to be removed after 10 years. Unlike the LNg IUDs, copper IUDs often result in heavier and longer menstrual bleeding, as well as they are effective immediately after insertion, meaning the birth control effect is in action right away.

Are there any risks?

The displacement or complete dislodging of the IUD is the most common complication, which should be addressed by a healthcare provider as soon as it is noticed. Less common complications include the rare possibility of unintended pregnancy, most often resulting in an ectopic pregnancy, which is when a fertilized egg grows outside of the uterine lining. It’s also possible to experience uterine perforation during the insertion process; however, having a trained professional insert the IUD lowers this risk. A common worry amongst women considering using an IUD is the risk of developing pelvic inflammatory disease. However, this risk remains low, with only a slight increase in risk during the first month after an IUD is inserted. Further, it is not the IUD itself that causes pelvic inflammatory disease but the contraction of a sexually transmitted infection (STI), which can progress to pelvic inflammatory disease. Most STIs can be treated with antibiotics without needing to remove the IUD.

How is an IUD inserted?

The process of getting an IUD begins with an individual talking to a healthcare provider about the various birth control methods, including the potential risk of complications, any side effects, and the positive aspects of each form of birth control. It is possible to have an IUD inserted on the same day as a consultation, provided that the individual has a negative pregnancy test. At this point, the healthcare provider may also complete a STI test to screen for any potential infections that should be treated; however, an IUD can still be inserted that day. After the healthcare provider examines the individual’s uterus, tools including a speculum and tenaculum will be inserted to allow the healthcare provider to see and straighten the cervix, before, the IUD is inserted into the uterus, working to prevent pregnancy.

Written by Megan Cisecki

References:

Bartholomew, S. (2009). What mothers say: The Canadian maternity experiences survey. Public Health Agency of Canada.

Black et al. (2016). Canadian contraception consensus (part 3 of 4): Chapter 7 – intrauterine contraception. Journal of Obsetetrics and Gynecology Canada, 38(2), 182-222.

Hubacher D. (2014). Intrauterine devices & infection: Review of the literature. The Indian Journal of Medical Research140(Suppl 1), S53–S57.

Lanzola, E. L., & Ketvertis, K. (2020). Intrauterine device (IUD). In StatPearls [Internet]. StatPearls Publishing.

Whaley, N. S., & Burke, A. E. (2015). Intrauterine contraception. Women’s Health, 759–767. 

Wildemeersch D. (2009). New intrauterine technologies for contraception and treatment in -nulliparous/adolescent and parous women. Facts, Views & Vision in ObGyn1(3), 223–232.

Image by Peggy und Marco Lachmann-Anke from Pixabay 

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