Final answer:
Placebo pills or sugar pills in birth control packs are hormone-free and trigger a lighter menstrual cycle when taken. Newer methods may eliminate menstruation altogether without adverse health effects.
Step-by-step explanation:
The placebo pills in birth control packs do not contain any hormones and are often referred to as sugar pills. These are typically found in the last week of the birth control pill pack, which include 21 active pills with hormones and 7 inactive ones. The active pills contain low-dose estrogens and progesterone which help in preventing pregnancy. When a person takes the placebo pills, the decline in hormones triggers menses, although the menstrual flow is lighter than usual due to reduced endometrial thickening. Some newer types of birth control are designed to be taken continuously, without the placebo week, thus eliminating menses entirely, which has no reported adverse health effects.