Passage: Starting in 2003, women have also been able to use a three-month version of the pill. Similar to the effect of using a constant-dosage formulation and skipping the placebo weeks for three months, Seasonale gives the benefit of less frequent periods, at the potential drawback of breakthrough bleeding. Seasonique is another version in which the placebo week every three months is replaced with a week of low-dose estrogen.

Question: What is a disadvantage of the birth control pill Seasonale?
breakthrough bleeding