The contraceptive effect of the minipill derives chiefly from the local action of the progestin on the uterus.

	The cervical mucus remains thick and acts as a barrier against penetration of the sperm.
	The cyclical thickening of the uterine lining is suppressed and its structure is altered in such a way that an egg cannot implant and grow.

In most women follicle maturation is not completely suppressed so that ovulation can still take place. The minipill is therefore less reliable than the combined oral contraceptive.

There is a new generation of minipills which suppresses ovulation in all women and is therefore more reliable. However, this is only achieved by increasing the progestin dose. Ask your doctor which type of minipill you are using.

The minipill does not provide protection against HIV or other sexually transmitted diseases.
If you want to have sex with someone you know little about you should use a condom.