Medical myths: You can't get pregnant when you're on the pill

Dr Max Pemberton 

Know your medical facts from myths? There are a lot of old wives' tales out there. But where do they come from and what is the truth? This week, does taking the pill really leave you immune to pregnancy?

Where did the myth come from?

There’s no doubt the invention of the oral contraceptive pill revolutionised women’s lives and enabled them to be in control of their fertility. But many people wrongly assume that it’s 100 per cent effective.

In fact, during one year, between five and eight women out of 100 taking the pill will fall pregnant (yet this rises to nearly 20 per cent for women who only use condoms). 


What's the truth?

Pregnant on the pill

No contraception can guarantee against pregnancy. The main reason the pill fails is because people don’t take it regularly—even missing one dose significantly increases the risk of falling pregnant.

It must also be taken at the same time each day to ensure a steady level of hormone in the blood. There’s some evidence that one antibiotic—rifampicin, used to treat TB—may affect the pill, so if you’re talking both you should discuss your options with your GP.


So, what's the answer?

A woman on the pill must endeavour to take it at the same time every day as prescribed. Missing doses is the primary reason why the pill isn’t 100-per-cent effective.

If doses are missed, then don’t assume you’re covered by just starting to take them again. Keep taking the pill but speak to your GP or health advisor and, until you do this, use an alternative form of contraception.