Just over 1 billion women – over a quarter globally – want to use contraception, according a 2021 World Organisation report.
Fortunately, there are a lot of choices for many women – in fact, there are more than 13 types of contraceptive methods and more than 200 brands of contraceptives worldwide. The vast majority of contraception in current use is hormonal, such as the contraceptive pill and implants and intrauterine devices.
However, women have different reasons for using birth control, only one of which may be to prevent pregnancy. Others include helping with painful or heavy periods, irregular cycles or acne.
Consequently, different women have different requirements for their contraception. Add to this other variables such as ethnicity, post-natal women, women in perimenopause, those taking other medications and the picture becomes even more complicated.
It's little wonder why women experiment with, on average, 3.4 different contraceptive methods throughout their lifetime, according to one US study.
The most common issue faced by women using hormonal contraceptives is the side effects, which can be so debilitating that they have no choice but to stop using it. These include migraines, blood clots, irregular persistent bleeding, nausea and changes in emotional states.
Women can spend years trying to determine which form of contraception suits them best. To complicate matters further, this can be an ever-changing situation as the female body goes through different hormonal states in life – from puberty, through to pregnancy and menopause – which leads to individual needs changing and possibly different reactions to the same medication over time.
Simply put: the contraceptives used need to be highly tailored to fit each individual’s requirements. And the emerging field of personalised medicine could be the answer.
It is rooted in the idea that unique and nuanced molecular, physiological, environmental and behavioural factors have an impact on how an individual may respond to a particular medical intervention.
Currently, personalised medicine does not often get applied specifically to women's health. However, this could soon change.
There is new research and technology that shows how contraception for women can be personalised – based on genetics and individual needs – so that it leads to fewer side effects and greater satisfaction.
Read more:
- The intriguing new science of how HRT could help women
- Is women's health really all that bad?
- Femtech: can technology predict ovulation, block period pain and stop incontinence?
In one of the first studies of its kind, researchers at Yale School of Medicine looked at how genes affect responses to hormonal birth control. They found a few genetic differences that might explain why some women have a higher chance of their birth control not working and why they experience certain side effects.
In particular, they found that a specific variant of a certain gene (known as CYP3A7) may increase the metabolism of the hormone etonogestrel, which is released by the contraceptive implant. For women with this variant, the hormone is broken down faster, meaning their implant won’t work as effectively.
It is estimated that this variant is found in roughly five per cent of the population, with these women more likely to experience a ‘contraception failure’ and fall pregnant.
Given we don’t currently carry out genetic testing pre-contraception counselling, we do not know which women will have the specific gene variant and so cannot predict how each individual will react to the implant. This could explain why some women fall pregnant despite using the contraception perfectly.
Then there’s weight gain. It can be a significant side effect of hormonal contraception, which is a major cause of women stopping its use. We now know a person’s individual genetics could here too play a major role: the same Yale School of Medicine team also found that a genetic variant in the oestrogen receptor gene (the ESR1 gene) is associated with significantly more weight gain when using the contraceptive implant.
All these insights are incredibly valuable and there may be breakthroughs in other areas, such as epigenetics. This basically describes factors beyond the genetic code, focusing on how DNA is modified – essentially, how genes are turned 'on’ and ‘off'. Learning more about this could help us better understand how women's reactions to hormonal contraception vary throughout their life course.
Overall, personalised medicine is a very young field of research with potential for huge impact, given the number of people using and needing hormonal contraception.
However, it now needs to expand significantly – as with all genetic research, a large number of people are needed in future studies to identify genetic variants. This is not only to provide further advances across this area, but also to deepen our understanding of female biology and how to most optimally provide women’s healthcare.
Read more: