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Female Hormone Contraception: Is It Time To Rethink?

April 30, 2021

Female health

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Recent news articles on the AstraZeneca vaccine for COVID-19 have been comparing the likelihood of developing blood clots from the vaccine with the instances of blood clots in women who are taking the combined oral contraceptive pill.

The latest data tells us that the chance of developing one of these rare blood clots from the AstraZeneca COVID-19 vaccine is about 4 in 1 million (0.0004%), yet the risk of developing a blood clot from the combined oral contraceptive pill (COCP) is 5 in 10,000 women per year (0.05%) – still low risk.

Focusing on the far higher risk of suffering blood clots as a result of the COVID-19 infection itself is probably more relevant, in order to make a fair assessment of the risk of clots (thrombosis) from the vaccination v infection. Thrombosis in patients admitted to hospital with COVID-19 has been reported as high as 48% [1].

Nevertheless, citing higher instances of blood clots in women taking the COCP compared to the vaccine raises some interesting questions. Understandably, the news about blood clots being a side effect of the COCP has worried many women and taken some by surprise as they claim they were not told of the risks by their GP

So, while easing the worries around the vaccination, it has increased concern amongst women about the combined oral contraceptive pill.

Is This Another Example Of Gender Bias In Medicine?

The rationale is clear, no drug is 100% safe and medicines we use every day carry the risk of side effects. But why is the media not using an equivalent comparison for a drug used only by men? Because there isn’t one.

Research on male hormone contraception is still being carried out but a solution is still several years away. This is despite an effective solution being found that is equivalent to the female oral hormonal contraceptive [2].  So why is it taking so long?

Could it be that the side effects are far worse? Well, so far, the side effects found with some types of injectable male contraception include acne, decreased libido, injection site pain, myalgia, and mood alterations [2]. One study was paused due to mood changes – but no mention of blood clots. 

Compare this to the side effects of the COCP according to the NHS website:

  • Headaches (first few months)
  • Nausea (first few months)
  • Breast tenderness (first few months)
  • Mood swings (first few months)
  • Increased blood pressure
  • Breakthrough bleeding and spotting (common in first few months)
  • Increased risk of serious side effects such as blood clots and breast cancer

Although more research is needed, it appears there are fewer and far less serious side effects for male hormone contraception than for women.

The reason it’s taking so long could, in part, be due to the fact that there is an effective female hormone contraceptive pill and societal and commercial demand just isn’t there for a male alternative. That in itself is unconscious gender bias – if men were the ones at risk of becoming pregnant would we have a solution faster?

The other question that needs to be answered is why regulatory health bodies around the world are reacting so rapidly to withhold or stop the use of the AstraZeneca vaccine (and now Johnson and Johnson)?  Yet the same authorities have not prohibited the use of COCP which carries a higher risk of blood clots compared to the vaccine. 

No causal link between these rare blood clots and the vaccines have so far been found. Yet 151 million women worldwide [3] are being prescribed the pill which does have a causal link to blood clots that pose a greater risk than the vaccine – albeit it still a low risk.

Why is it acceptable for women to carry the risk of blood clots from COCP and why isn’t more being invested to develop solutions to reduce the risk?

Is It Time To Rethink Female Hormone Contraception?

According to a UN report, 922 million women (or their partners) worldwide use some form of contraception.

Of these 24% use, female sterilisation compared to just 2% male sterilisation and is the most popular form of female contraception worldwide.

After female sterilisation, male condoms are the second most used form of contraception with the combined oral contraceptive pill being the 4th most popular form:

  • 24% use female sterilisation
  • 21% male condoms
  • 17% use IUD
  • 16% use the pill (aka COC)
  • 8% use injectable contraceptive
  • 2% use an implant contraceptive
  • 2% male sterilisation

What Is Female Contraception Doing To Women’s Bodies?

The natural fluctuation of female hormones during the menstrual cycle plays a key role in women’s overall wellbeing – it’s not just about fertility.

The 4 main female hormones – oestrogen, progesterone, LH, FSH – fluctuate naturally during a woman’s menstrual cycle, rising and falling during each phase to trigger ovulation and then a menstrual bleed if a woman doesn’t conceive. Each woman has a menstrual cycle that is entirely unique to her.

Menstrual cycle graph

There are receptors in the brain and other parts of the body that are affected by these hormonal variations, resulting in a range of physical and mental changes. This is especially true of the response hormones, oestrogen, and progesterone, produced by the ovaries.

These hormones have far-reaching effects not only on the female reproductive system, but on the nervous system, the musculoskeletal system, the digestive system, the cardiovascular system, the immune system, and metabolism.

Read more about the menstrual cycle>>

So what impact are these contraceptives having on the natural fluctuation of female hormones?

Female Sterilisation

Female sterilisation or tubal ligation is known to affect ovarian reserve thereby advancing the age of natural menopause [4]. In one study of women who underwent tubal ligation, it was found they were 10% more likely to report menopausal symptoms [5].

Combined Oral Contraceptive Pill

The combined oral contraceptive pill contains high level, artificial versions of oestrogen and progesterone and works by shutting down the internal production of female hormones (FSH, LH), which prevents ovulation (stopping the ovaries from releasing an egg) and stops the production of oestradiol and progesterone [6]. If you take a blood test from a woman taking the COCP all her hormones curves will be very low and flat, without fluctuations shown in the diagram above.

Progesterone Only Pill

The progesterone only pill contains progestins. Depending on the type, some suppress all the female hormones in the same way as the COCP. 

This type of progesterone-only pill has the following effects on a woman’s menstrual cycle:

  • Prevents follicular development
  • Prevents ovulation
  • Suppressed corpus luteum formation
  • Changes the nature of cervical mucus to inhibit the passage of sperms into the uterine cavity

A version of the progesterone-only pill called Depot Medroxyprogesterone Acetate (DMPA) which is an injectable form of contraception has been linked to the risk of osteoporosis in younger women [7].

This is because it decreases oestrogen production which is associated with decreased bone mass – this is why post-menopausal women are at a higher risk of developing osteoporosis. Not only that, but more recent studies have found that oestrogen may better protect women from respiratory viral infections such as covid-19.

Female hormonal contraception is disrupting the natural fluctuation of female hormones across a menstrual cycle. As these hormones play a vital role in women’s health, it’s important that women are made aware of the impact of any form of hormonal contraception on their health.

This needs to be weighed up against the risk of an unplanned pregnancy.  An unplanned pregnancy or unwanted pregnancy can cause huge psychological issues for women either by coming to terms with becoming a mother and having to adjust her life; or by making the decision to have an abortion which itself carries both physical (albeit low in developed countries) and mental health risks.


Female hormone contraception has been used for years and has revolutionised women’s lives by allowing them to take more control over their reproductive health.  

However, there is still a gender bias when it comes to contraception and it is the women who carry the burden and responsibility. It is women’s bodies that are impacted by hormonal contraception, causing disruption to the natural fluctuation of hormones that have a huge impact on their overall wellbeing.

It’s up to every woman to make her own choice about contraception, and do what is right for her, but to do so with the knowledge of the impact it’s having on her hormone health if she opts for hormonal methods.  But not only from the viewpoint of preventing unwanted pregnancies but to protect against sexually transmitted diseases as well.  Barrier methods are non-hormonal options and condoms are the only form of contraception to prevent sexually transmitted diseases.

More investment in hormonal contraception is needed and not just for women, but men as well. The risks to women’s health need to be reduced while protecting them from unwanted pregnancies.

Read Next: Menstrual Cycle: Tune Into Your Hormones>>

View More Female Health Articles>>

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This information has been medically written by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services