Your Birth Control Pill Is Classified as a Carcinogen

Millions of women around the world rely on birth control pills to prevent pregnancy. They are convenient, widely available, and often recommended by healthcare providers for family planning and other health reasons.

However, an important scientific classification by the International Agency for Research on Cancer (IARC), a branch of the World Health Organization, has raised questions about the relationship between some contraceptives and cancer risk.

Understanding this classification is important so women can make informed decisions about their reproductive health.

 

How Scientists Classify Cancer Risk

The International Agency for Research on Cancer evaluates substances and exposures to determine whether they can cause cancer in humans. These are grouped into different categories based on the strength of scientific evidence.

• Group 1: Carcinogenic to humans (strong evidence)

• Group 2A: Probably carcinogenic

• Group 2B: Possibly carcinogenic

• Group 3: Not classifiable due to insufficient evidence

These classifications do not mean a person will definitely develop cancer but rather indicate the level of evidence linking the exposure to cancer.

 

Combined Oral Contraceptives: Classified as Group 1 Carcinogens

Combined oral contraceptives (COCs) contain two hormones:

• Estrogen

• A progestogen (a synthetic form of progesterone)

  
  

These hormones prevent pregnancy mainly by:

• Stopping ovulation

• Thickening cervical mucus to block sperm

• Changing the uterine lining to prevent implantation

They are one of the most commonly used contraceptive methods globally because they are effective, convenient, and reversible.

Because of evidence linking their use with certain cancers, the International Agency for Research on Cancer classifies these contraceptives as Group 1 carcinogens (carcinogenic to humans).

Some common examples of combined oral contraceptives include:

• Yasmin

• Yaz

• Microgynon

• Marvelon

• Nordette

Research shows that the use of combined oral contraceptives is associated with an increased risk of certain cancers, particularly:

• Breast cancer

• Cervical cancer

• Liver cancer

  
  

Breast Cancer Risk

Some studies suggest that women who currently use combined oral contraceptives may have a slightly higher risk of breast cancer compared to women who have never used them.

However, this risk appears to decline after stopping the pills and gradually returns to baseline over time.

Breast cancer risk is also influenced by several other factors, including:

• Age

• Family history

• Genetic predisposition

• Lifestyle factors

Therefore, the pill is only one factor among many that can influence risk.

Cervical Cancer Risk

Long-term use of combined oral contraceptives has been associated with an increased risk of cervical cancer.

This risk appears to become more noticeable with use longer than five years.

However, cervical cancer is strongly linked to infection with human papillomavirus (HPV). Regular screening and vaccination play a major role in prevention.

Liver Cancer Risk

Research has also shown a possible link between long-term use of combined oral contraceptives and liver cancer, although this is considered relatively rare.

Liver cancer risk is also influenced by other major factors such as:

• Chronic hepatitis infection

• Alcohol use

• Liver disease

Emergency Contraceptives and Progestogen-Only Pills: Classified as Group 2B

Not all contraceptive pills fall into the same category.

Progestogen-only contraceptives (POCs) which contain only a progesterone-like hormone and no estrogen are classified differently.

The International Agency for Research on Cancer classifies these as Group 2B: possibly carcinogenic to humans.

This means that there is limited evidence of a cancer link, but the evidence is not strong enough to place them in the same category as combined oral contraceptives.

Examples of these progestogen-only or emergency contraceptive pills include:

• Postinor-2

• Postpill

  
  

These pills are commonly used as emergency contraception after unprotected sex to prevent pregnancy.

They work mainly by delaying or preventing ovulation, and they are usually taken within 72 hours after intercourse.

Because they contain only a progestogen, they fall into the Group 2B classification, meaning the evidence linking them to cancer is less certain.

The Other Side of the Evidence

Interestingly, research also shows that some contraceptive pills can reduce the risk of certain cancers.

Long-term use of combined oral contraceptives has been associated with a lower risk of:

• Ovarian cancer

• Endometrial (uterine) cancer

This protective effect may persist for many years after stopping the pills.

What This Means for Women

The classification of contraceptives by the International Agency for Research on Cancer does not mean women should panic or immediately stop using them.

Instead, it highlights the importance of being informed and discussing options with a healthcare professional.

Many factors influence cancer risk, including:

• Age

• Genetics and family history

• Lifestyle habits

• Duration of contraceptive use

For many women, the benefits of contraception—such as preventing unintended pregnancy and managing certain medical conditions—may outweigh the potential risks.

Final Thoughts

Birth control pills remain one of the most widely used and effective methods of contraception worldwide. However, scientific evidence shows that different types of contraceptives carry different levels of potential cancer risk.

Combined oral contraceptives containing estrogen and progestogen are classified as Group 1 carcinogens, while progestogen-only contraceptives and emergency pills such as Postinor-2 and Post Pill fall into Group 2B (possibly carcinogenic).

Understanding these classifications helps women make informed choices about their health, balancing benefits and potential risks with the guidance of qualified healthcare providers.