The Progesterone Only Pill (POP) - often referred to as the mini pill only has one type of hormone in it - progesterone. It is a medicine that can be used when the Combined Pill is not suitable.

Used as a form of contraception to prevent pregnancy.

The progesterone in this pill causes changes to the cervical mucus and lining of the womb to make the environment less hospitable for an egg to implant. I some woman the progesterone pill will stop ovulation. If it is taken with out any mistakes it is 99% effective.

The dose of the progesterone hormone in different POPs can vary but the important thing is that you take one tablet a day. Due to there being several different types of progesterone in different POPs there are sometimes slightly different instructions - some POPs must be taken within a 3 hour window, and some have a 12 hour window. The safest thing to do is to make sure you take the POP at the same time every day.

If you do take it late (after 3 hours for some, after 12 hours for others) then it is considered a missed pill and you might need to take steps to ensure you are protected from pregnancies for the next three days.

One of the commonest side effects of starting the POP is some irregular bleeding, however it is also possible for periods to become lighter or stop altogether. If you do suffer with irregular bleeding after starting the POP it usually settles down after 2 to 3 months.

Other side effects include breast tenderness, headaches and worsening acne. These also often settle down after the first few months.

It's very important to avoid missing a pill.

Alcohol doesn't stop the pill from working but it may interfere through causing vomiting or forgetting to take the pill at the right time of the day.

There is no evidence that taking the POP while pregnant causes any harm to the baby. However if you do become pregnant there is a greater chance of the pregnancy being an ectopic pregnancy - this is a pregnancy developing outside of the womb - and this is a serious condition. It would be very important to seek urgent advice if you were suffering from sudden unexpected lower abdominal pain and bleeding.

It is safe to take the POP while breastfeeding.