Here’s How Birth Control Works and When You Should Take It!
Medically Reviewed by Dr. Nicole Avena

Contraceptives have come a long way since the first birth control pill was introduced to the public in 1960. Today, roughly 65% of women in the U.S. between the ages of 15-49 use some form of birth control.

If you’re one of them, it’s important to understand how your contraceptive is affecting your body beyond preventing pregnancy.

All forms of birth control – including hormonal contraceptives such as the birth control pill, implants, some intrauterine devices (IUDs), injections, vaginal rings, and skin patches – may pose certain health risks. The synthetic hormones they use may not be for everybody. They can tinker with your body’s hormonal balance and even lead to physical and emotional problems.

This is particularly concerning when you consider that the birth control pill is the most commonly prescribed form of contraception in the U.S. Approximately 25% of women aged 15 to 44 who currently use contraception report using the pill as their method of choice.

How Birth Control Pills Work

It’s easy to understand why the birth control pill is so popular. You simply take one pill orally a day, and that’s it.

If you’re fully compliant, it’s 91 to 99% effective at preventing pregnancy, and its convenience allows for spontaneous sex. At any time, you can stop taking the birth control pill and your menstrual cycle will return to normal, usually within a few months.

Hormonal contraceptives such as the birth control pill work by using synthetic female sex hormones (estradiol and progestin) to manipulate your reproductive cycle and prevent pregnancy.

There are two types:

1. The Combination Pill is the most-used type. It contains both synthetic estrogen (estradiol) and progesterone (progestin). This pill is taken once a day. It’s the most common birth control pill.
2. The Progestin-Only Pill, also called the “mini-pill,” only contains progestin. It’s often prescribed when estrogen is a problem for an individual. Like the combination pill, it’s also taken once a day. However, it needs to be taken at the same time every day.

When you take the pill, estradiol and/or progestin enter the brain and act as endocrine disruptors, interfering with the signaling process that triggers ovulation.

Specifically, the hormones stop the hypothalamus from directing the pituitary gland (your hormone regulator) to secrete the hormones that facilitate ovulation (the readying and release of an egg from one of the ovaries).

The progestin component additionally thickens the cervical mucus, making it relatively impenetrable to sperm, and causes the uterine lining to thin – inhibiting implantation in the rare event an egg is fertilized.

Many birth control pills will include a week of placebo pills that trigger monthly withdrawal bleeding in the absence of the hormones. It’s much lighter and shorter than a regular menstrual period.

Placebo pills aren’t medically necessary, but the withdrawal bleeding that results from taking them provides confirmation that no pregnancy has occurred. Still, some women (under the direction of their physician) elect to take continuous birth control pills with no placebo and avoid the withdrawal bleeding altogether.

Oral contraceptives may be prescribed to help or resolve other conditions unrelated to protection against pregnancy such as:

• Heavy flow
• Pain and cramping
• Irregular periods
• Premenstrual syndrome (PMS)
• Problems with the endometrium
• Polycystic ovary problems
• Fibroids

Oral contraceptives can offer benefits beyond birth control. They may also:

• Reduce heavy menstrual bleeding, painful periods, and anemia.
• Allow you to have periods less often than once a month.
• Lower risk of serious health issues of the colon, ovaries, and endometrium (monthly thickening of uterine lining).
• Help improve acne, migraines, and irregular periods.

Cautions for Birth Control Pills

The combination pill and mini-pill come with different concerns. Discussing them with your medical doctor can help you determine if oral contraceptives are right for you, and which one may be best.

Hear are the general cautions that come with birth control pills:

Combination Pill Cautions

According to Harvard Health, the combination pill is generally considered safe except for women who meet any of the following criteria:

• Currently breastfeeding
• Over age 35
• Smokers
• Have a history of blood clots, breast health, or endometrium issues; heart health problems, stroke, or elevated blood pressure; liver health problems; migraines; blood sugar issues; or auto-immune health issues such as lupus.

Side effects are usually short-term and may include:

• Breast tenderness
• Headache
• Nausea
• Weight gain

The Mini-Pill Cautions

The mini-pill, on the other hand, is a safe choice for women who may meet any of the following criteria:

• Have problems with estrogen
• Are breastfeeding
• Are over 35
• Smokers
• Have had issues with stroke or lupus

However, it should not be taken by women who meet may:

• Have had serious breast health issues in the last five years.
• Have had any form of serious liver problem.
• Take certain seizure medicines.

Side effects may include:

• Acne
• Headache
• Breast tenderness
• Mood changes (low mood, greater emotionality)

Lesser-Known Birth Control Concerns

Here are some of the lesser-known birth control cautions linked to oral contraceptives that your primary care provide may not tell you about:

Disrupted Hormonal Balance

Synthetic progesterone (progestin) isn’t a perfect match to the natural progesterone you have in your body. Consequently, it can bind to other receptors besides progesterone receptors in your body. This cross-reactivity can lead to consequential hormonal imbalances.

Specifically, when a synthetic hormone binds to the incorrect receptor, that receptor can miscommunicate signals, which can cause other inaccurate signals and throw off hormonal balance. Thus, synthetic hormones may cause hormonal imbalances and negative side effects. This doesn’t happen to all women, but may cause problems for some.

For example, research from UCLA published earlier this year noted elevated cortisol levels and lower testosterone levels associated with oral contraceptive use, suggesting users may be at greater risk for lower sex drive, brain health issues, and mental health problems.

The researchers believe that the effects may be because synthetic hormones in some contraceptives bind more to androgen receptors – sites in the body where testosterone usually binds, causing a greater inflammatory stress response in some users.

Problems with Low Mood and Brain Maturation

The following studies indicate potential risks with early use of birth control pills.

New animal research presented in 2023 by scientists from The Ohio State University examined the effects of synthetic birth control hormones on the prefrontal cortex (PFC) – the area of the brain that manages impulse control and develops throughout adolescence.

When given synthetic hormones just after puberty, the subjects exhibited greater impulsivity later, suggesting that synthetic hormones possibly stall PFC maturation. The hormones were found in brain tissue as well.

Although speculative at this point, and not fully understood, the scientists concluded that this is the first evidence to indicate that commonly used birth control hormones administered during a vulnerable developmental period (adolescence) may influence PFC development, which could contribute to altered judgment and greater risk-taking.

A 2023 study found that adolescents/teens who began using oral contraceptives at or before the age of 20 years had a 95% increased risk of low mood in their first two years of birth control use compared with peers who never used oral contraceptives. It also found an association between adolescent birth control pill use and a higher risk of low mood later in life.

Additionally, a Danish study involving 1 million women found an increased risk for first use of medication for low mood and first diagnosis of low mood among users of different types of birth control pills, with the highest rates among adolescents.

Long-term Birth Control Use

A review analysis of research indicated that using birth control pills for more than five years is associated with greater risk of breast health problems in individuals genetically predisposed to serious breast health problems.

Changes to Brain Structure

The hypothalamus in women taking the birth control pill was roughly 6% smaller than in women who weren’t taking the pill, a 2019 study found. The hypothalamus is an area of the brain that produces hormones that moderate heart rate, body temperature, appetite, and mood.

Sex hormones have been shown to promote the growth of neurons. Scientists theorize that the synthetic hormones in oral contraceptives may interfere with this type of growth, leading to less brain cell growth.

Autoimmune and Gut Health Issues

Oral contraceptives are linked to gut health and autoimmune issues. Of course, when your gut health is disrupted, it also affects the brain and nervous system as the gut is lined with neurons and communicates continuously with the brain.

Be Your Own Advocate

If you or someone you love is considering taking birth control pills, or any other hormonal contraceptive, be sure to discuss the potential health concerns with your medical doctor – including how they affect hormonal balance, the brain, and mood so that you can make informed decisions about your health.

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These statements have not been evaluated by the FDA. This content is for informational purposes only. It is not meant to substitute for medical or healthcare advice from a physician, nor is it intended to diagnose, treat, cure, or prevent any disease. Consult your healthcare provider before beginning a new health regimen.

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