All of the statements regarding progesterone only pill are true, except
Inhibits ovulation
Failure rate is the same as combined OCP
Irregular bleeding is a known complication
Acts by altering the cervical mucous
Failure rate of combined OCP is 0.2/100 women years, whereas failure rate of progesterone only pill is about 0.5 - 2 per 100 women years of use. Progesterone only pill acts by thickening cervical mucous, causing atrophy of endometrium or by inhibiting ovulation.