What is emergency contraception, and how does it work?

In this article below, highly esteemed consultant gynaecologist, Ms Michelle Swer, talks to us in expert detail with regards to emergency contraception. 

What is emergency contraception, and how does it work?

Emergency contraception is contraception that is given to reduce the risk of pregnancy if someone has had unprotected sexual intercourse (UPSI). Below explains how they work. It varies depending on which one you choose.

Can you provide an overview of the different types of emergency contraception available?

There are 3 options available:

1. Copper intrauterine device (IUD) is the treatment of choice as it works up to 120 hours after UPSI or within five days of the earliest expected ovulation and has the lowest failure rate (less than 1%). It also gives ongoing contraception. It works by preventing implantation. However, it is an invasive procedure and may not be readily available.
2. Levonorgestrel (Levonelle) oral tablet works up to 72 hours after UPSI and has a failure rate of 1.7 – 2.6%. This is commonly available over the counter through any pharmacy (costs approximately £25). It works by delaying or preventing ovulation.
3. Ulipristal acetate (ellaOne) is also an oral tablet and works up to 120 hours after UPSI. This also works by delaying or preventing ovulation. Failure rate is 0.9-1.7% and the cost is £25 over the counter.

How effective is emergency contraception in preventing unintended pregnancies?

Emergency contraception will be effective in over 95% of cases if taken at the appropriate times. The Copper IUD is the most effective with less than 1% chance of not preventing unintended pregnancies.  The closer to the time of unprotected intercourse the method of contraception is taken, the more effective it is.

You should also think about ongoing contraception and may wish to discuss this with your doctor at the same time. A pregnancy test is also a good idea 3 weeks from UPSI to confirm that you are not pregnant. Unprotected intercourse may also put you at risk of sexually transmitted infections (STIs) and you may wish to request testing for this.

If you are taking an emergency contraception due to a missed pill, you will need to use additional contraception for seven more days for Levonelle and 14 days for ellaOne (unless using Qlaira where you need to use additional contraception for between nine to 16 days respectively).

What are the time limitations for using emergency contraception after unprotected sex or contraceptive failure?

The Copper IUD works for up to 120 hours after UPSI or within 5 days of the earliest expected ovulation. Levonelle (oral tablet) works up to 72 hours after UPSI. Ullipristal (oral tablet) works up to 120 hours after UPSI.

Are there any specific factors that may affect the effectiveness of emergency contraception?

When taking oral emergency contraception, vomiting within three hours of taking it makes it less likely to be effective and the advice would be to take another tablet.  Persistent vomiting makes it less likely that the emergency contraception will work.

With regards the use of coil as emergency contraception it is less likely to be effective if not placed correctly or if it is low lying in the cavity. A coil check is advised six weeks after, especially if the plan is to continue using this as long-term contraception. Timing is important so using the emergency contraception as close to the time of unprotected intercourse makes it more effective.