Question:

I had unprotected sex after forgetting to take one contraceptive pill and took the morning-after pill 20 hours after the unprotected sex. How effective is the morning-after pill and how soon can I take a pregnancy test?

Answer:
Unfortunately the morning-after pill is not 100 percent effective. Other than celibacy, no contraceptive will protect you from pregnancy entirely. Each have their pros and cons and it's important to consider all variables.

Specifically with the "morning after" options, there are three methods available in Australia, including the progesterone-only method, combined pill (oestrogen and progesterone) and IUD insertion.

The progesterone-only method works by delaying/preventing ovulation, by preventing a fertilised egg from implanting in the uterine wall, or by interrupting the production of hormones needed for pregnancy to continue. It is best used within 72 hours of unprotected sex. It can be taken up to 120 hours after unprotected sex but it loses effectiveness after 72 hours.

The instructions are to take the two pills together or separate each by 12 hours. Taking it together is easier and newest research suggests that it is just as effective when taken at the same time. It has been shown to be 95 percent effective when taken correctly in the first 24 hours and 89 percent effective if taken up to 72 hours after sex.

As such, it is important to try to take it as quickly as possible. The longer the delay, the less effective it becomes. The best part of this treatment is that it is available from pharmacies without prescription so access is easy. But make sure you don't rely on it as a regular contraceptive — it is designed to be used in emergency situations.

The combined pill preparation has been used for decades and is not used much anymore. It tends to make women very nauseous and can cause vomiting so the progesterone-only method is preferred. Additionally, it requires a visit to the doctor for the prescription, which causes accessibility issues as well.

IUD insertion is generally only used in special circumstances because once it has been placed internally, it is designed to be there as a long-term method. As such, it is not the preferred choice by most people.

Pregnancy tests can either assess the blood or urine of a woman. Both tests measure the amount of the pregnancy hormone, human chorionic gonadotropin (HCG).

Blood tests can measure much smaller amounts of HCG, and so can detect pregnancy earlier than urine tests. They can pick up HCG levels just after implantation of the embryo, typically seven days after ovulation. You will need to see your doctor to organise this blood test but most will wait until you've "missed your period" (ie, two weeks after ovulation).

If you conduct a home pregnancy test it will detect the amount of HCG present in your urine. The HCG level has to reach a certain level to be detectable to give you a positive result so often women need to wait until they've missed their period. Please note that a test may be negative for urine test if you're not pregnant, if ovulation occurred later than you thought or the HCG levels are very low. Regardless, it's important that you see a GP to confirm the pregnancy and assess the situation with you.

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