Can you get pregnant on the pill?
The simple answer is yes. No form of contraception (birth control) is 100% effective. However, if taken perfectly, the contraceptive pill (also known as the combined contraceptive pill or simply “the pill”), is a highly effective method of contraception. More than 80% of sexually active women will become pregnant within a year if they do not use any method of birth control.
So, what are the statistics on the pill?
How reliable is the pill?
The pill is a very reliable form of birth control if it’s used correctly all the time- but in reality, most women tend to miss a pill or make mistakes from time to time, which reduces the reliability.
- Around 0.3% of women who use the pill perfectly will become pregnant each year
- Around 9% of women will become pregnant if they take the pill correctly most of the time. As most women fall into this category, essentially this means the pill is 91% effective.
How does the pill work?
The combined oral contraceptive pill works by stopping ovulation. It is taken daily for 21 days in a row, then 7 inactive or “sugar pills” are taken, during which a woman will usually get a withdrawal bleed, like a period. Some women may decide to skip the week of sugar pills and take packs of active pills back-to-back instead. This can be done for several months at a time to avoid having periods.
What causes the pill to fail?
A variety of things can cause the pill not to work properly (which can obviously lead to pregnancy). Common issues include:
- a late or missed pill (or pills)
- vomiting or diarrhoea
- some prescription drugs including HIV medications and Epilepsy medications may interfere with the pill (always check the label if you’re taking any other treatments or ask your doctor or pharmacist , to make sure this is not the case).
- most antibiotics are OK to use with the pill, but rarely used antibiotics used in the treatment of TB and meningitis are not.
- some over the counter medicines or supplements (such as St John’s Wort)
How effective is the pill compared to other forms of contraception?
No method of contraception is 100% reliable, and some forms of birth control such as the pill are affected by how carefully a woman follows instructions for correct use. Effectiveness is usually stated as the percentage of women who become pregnant after one year of using that method.
- The mini pill or progesterone only pill (POP) is said to be 91% effective, based on typical, less-than-perfect use (i.e. about 9% of users will become pregnant per year). This is about the same as the combined contraceptive pill. Both forms of pill are 99% reliable if taken “perfectly”, but perfect use is not the reality for most women!
- The progesterone “depo injection” is a long acting option, which lasts 12 weeks. It’s said to be about 94% effective (i.e. about 6% of users will become pregnant each year).
- IUDs including the hormonal IUDs and copper coil are over 99% effective.
- The progestogen implant , commonly known as the “rod”, is more than 99% effective.
- The contraceptive vaginal ring is about as reliable as the pill, at 91%.
- Condoms are about 82% effective.
- Tubal ligation or occlusion (forms of female sterilisation) are more than 99% effective.
For more information about different forms of contraception, check out our contraception hub page.
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