According to the US Department of Health, 9 per cent of people who take birth control pills will become pregnant each year.
There are two main types of pill which vary in hormone content and the way they work.
The most widely used are the combined pills which have two hormones, oestrogen and progestogen.
There are also progestogen-only pills which have progestogen only and no oestrogen.
There are two types of progestogen-only pills available in Ireland, Noriday and Cerazette, which differ in the way they work and instructions for what to do if you miss a pill.
Other methods of contraception that use hormones include vaginal rings, patches, subcutaneous implants, injections, and some IUDs.
The pill boasts an impressive efficacy (99.7%) but may lead to pregnancy if not taken correctly. It goes without saying that the average woman will miss a dose occasionally or take it at the wrong time.
Here's what to do if that results in pregnancy:
Because accidental pregnancy is fairly common from failed or misused hormonal birth control, many developing embryos may be exposed to high levels of progestin and/or estrogen early on in pregnancy.
However, research indicates that this will not cause major problems for your health or the health of your embryo.
For example, a 2016 study published in BMJ found that there was no link between taking birth control pills while pregnant and having a baby with birth defects.
However, it is recommended that you stop taking them.
If you get pregnant with an IUD (Intrauterine Device), it's important to see a doctor and have it removed as soon as possible – as it can lead to complications during pregnancy.
For more information, contact the Irish Family Planning Association (IFPA) Appointment Line on 1850 49 50 51.
Main image by @ashleygraham