Birth Control Pills: A Guide

Birth control pills are one of the most popular forms of contraception. Also known as oral contraceptives, these capsules are taken orally and used to prevent pregnancy. How do birth control pills work? They contain hormones, specifically progestin and estrogen, which prevent ovulation and the thickening of the endometrium (more on why this matters later).

Choosing to take birth control pills is a personal choice that should be made in with the assistance of a gynecologist. The following is not medical advice and is entirely meant for informational purposes.

• Definition
• Types
• How They Work
• Effectiveness
• Side Effects
• Missing a Birth Control Pill

Related article: "What Is Plan B?" 

What Are Birth Control Pills?

Birth control pills, also known as oral contraceptives, are a common method for preventing pregnancy used by women. These capsules may do one or all of three things:

1. Prevent the female body from ovulating, i.e. from releasing an egg to be fertilized.
2. Thicken the cervical mucus, which makes it more difficult for the sperm to reach an egg and fertilize it,
3. Thin the endometrium, which is the uterus lining where an egg lodges after fertilization.

They do this through a combination of hormones, including estrogen and progestin, and placebo pills. There are three different types of oral contraceptives, which work in slightly different ways but all have the same goal: preventing pregnancy.

2 Types of Birth Control Pills

There are 2 main kinds of oral contraceptives: combination pills and progestin-only pills.

1. Combination Birth Control Pills

These contain progestin and estrogen. Unlike progestin-only capsules, most of these capsules contain hormones of varying doses. Combination pills accomplish two things:

1. They prevent ovulation, which is when the ovaries release an egg to be fertilized.
2. They thicken the cervical mucus, which helps prevent the sperm from reaching the uterus to fertilize an egg.

There are three types of combination birth control pills:

1. Monophasic: One-month cycle capsules that contain the same dose of hormones, except for the last week of the month during which the user takes placebos and has their period.
2. Multiphasic: One month-cycle capsules that contain different doses of hormones. Similarly to monophasic oral contraceptives, multiphasic birth control has one week of placebo pills.
3. Extended-cycle: 13-week cycle contraceptives. 12 weeks contain capsules with active hormones and the 13th week contains placebos. With this type of birth control, the user has their period 3–4 times annually.

Examples of combination birth control: Levlen, Estrostep, Levora, Natazia, Mircette, Yasmin, and Yaz.

2. Progestin-Only Birth Control Pills

As their name would suggest, these do not contain estrogen — only progestin. All capsules in this type of contraception are active, meaning that people who take progestin-only birth control pills may never menstruate. Progestin-only options are sometimes called “the minipill.”

These work differently than combination alternatives. Progestin-only capsules thin the endometrium and thicken the cervical mucus. THis accomplishes two things:

1. By thinning the endometrium lining, it becomes harder for a fertilized egg to implant and grow.
2. By thickening the cervical mucus, it helps prevent sperm from reaching the uterus in the first place.

Progestin-only contraception may be a good option for women who cannot take estrogen for health reasons.

Examples of progestin-only birth control: Camila, Errin, Micronor, Jolivette.

Birth Control Pills Effectiveness

The birth control pill is 99% effective with perfect use, i.e. when taken every day. With typical use, they’re approximately 91% effective for both progestin and combination types.

By comparison, the birth control implant is 99% effective with perfect and everyday use. Unlike a capsule, the implant is inserted into the arm, meaning that you can't forget to take it.