How emergency contraception works — and when it won’t

NO matter how careful you are, sometimes mistakes happen, and when they happen during a night of passion, there’s relief in the morning after pill. But this emergency contraceptive, also called Plan B, won’t work sometimes, and it’s important that you know when it won’t.

In essence, this pill is used to prevent pregnancy in women who have had unprotected sex, or whose birth control method — like the barrier condom method — failed.

The morning after pill has as its main ingredient Levonorgestrel, an artificial hormone that can prevent pregnancy by delaying ovulation and preventing implantation of a fertilised egg. The method involves ingesting two pills, the first of which should be taken within 72 hours or three days of intercourse.

While for the most part the pill will work to prevent pregnancy, there are also instances when it won’t, or may not.

These include:

1. After more than 72 hours

The pill is more effective the sooner it is taken. Levonorgestrel works by preventing ovulation (if it hasn’t already happened) and closing off the cervix to prevent the sperm from getting into the uterus. While some brands in other countries allow up to 120 hours (five days), those available locally only guarantee a certain amount of protection up to three days.

2. If you are ovulating

Morning after pills work by temporarily stopping your ovary from releasing an egg — like pulling the emergency brake on ovulation. The pills won’t work if your body has already started ovulating.

3. If you are already pregnant

The pill will not work if you are already pregnant, even if you don’t know yet. The hormone in the morning after pill cannot cause an abortion, nor does it have any significant impact on an existing pregnancy.

4. If you throw up after taking it

One of the most common side effects of using the morning after pill, or any other hormonal preparation, is nausea. This means that it is not uncommon for a woman to throw up immediately after taking the pill. If this happens when taking either of the two pills in the packet, it is strongly advised that you take another dose.

5. If you have certain diseases

Certain diseases like Crohn’s disease might impair the efficacy. The morning after pill may also be less effective and have adverse reactions in people with liver disease, or any other illness that inhibits how the body processes food and medicine, such as Porphyria. Allergic reactions may also occur.

6. If you are taking certain medications

Epilepsy drugs, anti-fungal drugs (eg for yeast infections), antibiotics and even natural herbs like St John’s wort may also cause the pill to be less effective. Chemicals in some medications, and even natural herbs, can interfere with how the hormone in the pill works, and even how the other medications work.

7. Eleven per cent of the time

Even when taken correctly within 72 hours after sex, Levonorgestrel is still only proven to be 89 per cent effective in preventing pregnancy. It is not as reliable as contraceptives that are recommended for regular use such as the male condom, an intrauterine device (IUD), the pill or the Depo Provera injection. The emergency contraceptive pill should therefore not be used as a regular method of birth control.

According to physician Dr Lincoln Wright, there are other types of emergency contraception.

“One of them is Depo Provera — this is an injection that you administer in the arm or in the buttocks and it prevents the implantation of any fertilised egg into the endometrium [the lining of the uterus]. The morning after pill is the same principle — it prevents fertilisation of the egg and subsequently there will be no implantation.”

Adding that Depo Provera is often used in women who have been raped, Dr Wright explained that once taken within two days after unprotected intercourse, it prevents implantation of the egg by altering the lining of the uterus.

IUDs can also be used to prevent pregnancy.

They work by preventing implantation of the pregnancy in the womb. It has the advantages of being used up to five to seven days after unprotected sex, offering long-term reversible contraception at the same time — five to 10 years. The main drawback is that you have to find your doctor or a nurse to have it inserted.

Note that if for some reason you can’t or don’t want to go to the nearest drugstore and pick up the morning after pill, you can actually use the regular oral contraceptive pill as emergency contraception.

The amount of pills that you should take will depend on the brand of pill that you have and you should speak with your doctor about the dosage.