There are no estrogen side effects with the mini-pill. The amount of progestin in mini-pills is less than in combined pills. Mini-pills are easier to take. You take exactly the same kind of pill every single day. Nursing mothers can take progestin-only pills, preferably after the baby is 6 weeks old.
Menstrual irregularity is the most common problem with mini-pills.
While there is less blood loss, bleeding may be at irregular intervals and there may be spotting between periods. Mini-pills tend to make periods short and scanty. You may go several months with no bleeding at all. You have to remember to take a pill every single day. The failure rate with mini-pills is a bit higher than with combined birth control pills.