The combined oral contraceptive pill, more commonly known as ‘the pill’, is a popular contraception method for many women. Typically you take one pill every day for 21 days, followed by a 7 day break when you have a bleed similar to a period. The hormones in the pill work to prevent ovulation and thicken cervical mucus to help stop sperm reaching an egg.
But can you still get pregnant even if you’re taking the pill correctly? Let’s take a look at how effective the contraceptive pill is and what can cause it to fail.
How the contraceptive pill prevents pregnancy
The pill contains synthetic versions of the female hormones oestrogen and progesterone. It works in several ways:
- Prevents ovulation – Stops your ovaries from releasing an egg each month for fertilisation
- Thickens cervical mucus – Makes it harder for sperm to reach the womb and fertilise an egg
- Thins the womb lining – Can prevent implantation of a fertilised egg
When taken properly, these actions work together to stop pregnancy happening.
Typical and perfect pill use
No contraception is 100% effective. With typical pill use, around 9 women out of 100 will get pregnant in a year of use. However, with absolutely perfect use, less than 1 women in 100 will get pregnant in a year.
Typical use accounts for common human errors like forgetting to take your pill or occasionally taking it late. Perfect use means taking the pill consistently, at the exact same time daily, without ever missing one.
In real life, achieving perfect pill use can be challenging. But you can maximise your chances by setting a daily reminder and linking it to an existing routine like cleaning your teeth. If you find yourself regularly missing pills or taking them at different times, speak to your doctor about switching to a more appropriate contraceptive option for your lifestyle.
What to do if you miss a pill
If you do miss a pill, take it as soon as you remember, even if it means taking 2 pills in one day. Missing 1 pill is not likely to have a major impact on contraceptive efficacy, but missing 2 or more pills in a row significantly raises your risk of pregnancy.
Always refer to the instructions that come with your pill pack if you miss any, as advice can vary between brands. If you have had unprotected sex and miss more than 1 pill, speak to your doctor about emergency contraception.
Can other medications affect the pill?
Some medications can interfere with how the contraceptive pill works when taken at the same time. These include:
- Antibiotics like rifampicin
- Anti-epilepsy medicines like carbamazepine
- St John’s Wort (a herbal medicine)
- Laxatives and anti-sickness medicines
Always check with your doctor or pharmacist before taking any new medications alongside the pill. You may need to use additional contraception while taking that medicine and for a short time after.
What if you’re sick while on the pill?
If you vomit within 3 hours of taking your pill, it’s unlikely to have fully absorbed. Take another as soon as possible and continue as normal. If you continue being sick, use additional contraception and speak to your doctor.
Severe diarrhoea can also reduce pill absorption. Follow the same advice as above if this happens to you.
Considering alternatives to the pill
There are many contraceptive options besides the pill, including:
- Contraceptive implant – inserted into your arm and lasts 3 years
- Contraceptive injection – an injection every 8-12 weeks
- Intrauterine system (IUS) – inserted into the womb and can last 5+ years
- Contraceptive patch – a patch on your skin changed weekly
- Vaginal ring – inserted monthly and left in place for 3 weeks
If taking a daily pill is proving problematic, one of these longer-acting reversible contraceptives may suit your lifestyle better. Discuss your options at your next sexual health screening or contraceptive review appointment.
Additional information
- With typical use, around 9 out of 100 women will get pregnant using the pill over 1 year
- Perfect pill use is crucial – take it at the exact same time every single day
- Even 1-2 hours late can increase pregnancy risk
- Speak to your doctor if you regularly miss pills or take them late
- Consider longer-acting alternatives like the implant if the pill doesn’t suit your lifestyle
Photo “The Pill” by Anthony Cunningham for Zoom Baby
Zoom Baby is a leading supplier of Pregnancy Tests and Ovulation Test Kits
