Daily Bulletin

The Conversation

  • Written by Deborah Bateson, Clinical Associate Professor, Discipline of Obstetrics, Gynaecology and Neonatology, University of Sydney

About one-third of people using contraception use the pill. But how effective is it?

There are two types of contraceptive pill – the combined pill, containing oestrogen and progestogen, and the progestogen-only-pill (often referred to as the mini-pill).

While most evidence about pill effectiveness relates to the combined pill, both pill types are quoted as being 93% effective in typical use and 99.5% effective in perfect use.

So what do these figures mean and how were they derived?

Read more: How to choose the right contraceptive pill for you

Do you use the pill ‘perfectly’?

To test the efficacy of the pill, women were enrolled in studies and instructed to take their pill at the same time every day. Perfect use was calculated from those who stuck to study rules by never running out of pills, never missing a day, and not taking any medications that can decrease the pill’s effectiveness. The studies assumed the women were all equally fertile and “at risk” of pregnancy.

Under these strict conditions both pill types were around 99.5% effective. This means within a 12 month period, five out of a thousand women could be expected to become pregnant.

But, most people’s lives do not reflect perfect research conditions and it’s more realistic to consider effectiveness in “typical use”. Both pill types have typical use effectiveness of 93% which means seven users in every 100 become pregnant in a 12 month period.

The lower rate of 93% reflects everyday life where pills may be missed, packs run out with no time to get a new prescription, pills are not absorbed because of vomiting or diarrhoea or the pill’s effectiveness is reduced by another medication (including some common herbal over-the-counter preparations such as St John’s Wort).

In reality, the probability of pregnancy is likely to lie somewhere between the 93% and 99.5%. And effectiveness may improve over time as users become more accustomed to taking the pill every day.

How effective is the pill? Most people won’t be able to consistently take the pill at the same time each day without fail. from www.shutterstock.com

Effectiveness can be increased by also using condoms (which have the added advantage of preventing sexually transmissible infections), and by using emergency contraception if pills are forgotten.

Read more: It's OK to skip your period while on the pill

Timing is everything

The combined pill primarily works to stop the release of an egg from the ovary each month. While a routine of same-time daily pill-taking is important, the combined pill will continue to be effective if it’s taken up to 24-hours late as ovulation will continue to be prevented.

The less commonly prescribed progestogen-only pill mainly works by thickening the mucus at the cervix to prevent sperm from swimming up into the uterus and fallopian tubes to fertilise an egg.

This effect wears off after approximately 27 hours, which means it needs to be taken within a narrow three-hour window each day. For this reason, the progestogen-only-pill is more likely to sit towards the lower 93% mark than the upper level of 99.5% compared to the combined pill.

Women in their teens and early twenties are likely to have a higher pill failure rate than older users. This might be because they’re more fertile, or because they have more trouble remembering to take the pill each day and fill their repeat prescriptions.

For this reason the progestogen-only-pill is rarely prescribed for this age group and more effective methods such as an implantable contraceptive device or a combined pill are generally recommended.

As a general rule, the less the contraceptive user needs to do in order to make it effective, the more effective it’s likely to be. The long acting reversible contraceptives (LARCs) are recognised worldwide as the most effective methods because they don’t depend on human behaviour once they’re put in.

How effective is the pill? An intrauterine device can be implanted and can last for up to ten years. from www.shutterstock.com

LARCs include the contraceptive implant which lasts for up to three years and the hormonal or copper-intrauterine devices (IUDs) which last up to five and ten years respectively.

They are 99.5-99.95% effective because once inserted there is no need for the user to remember to do anything on a regular basis, which can make them an attractive alternative to the pill for those wanting a reliable method.

Read more: Don't want to take a contraceptive pill every day? These are the long-acting alternatives

Side-effects, risks, costs and additional benefits are just some of the other features that influence how women choose which method of contraception to use, in addition to effectiveness. Understanding what effectiveness means and how it is calculated is an important step towards making an empowered choice.

Authors: Deborah Bateson, Clinical Associate Professor, Discipline of Obstetrics, Gynaecology and Neonatology, University of Sydney

Read more http://theconversation.com/how-effective-is-the-pill-122189

Writers Wanted

No Barnaby, 2050 isn't far away. Next week's intergenerational report deals with 2061


Tips For Good SEO In The Law Sector


The Conversation


Prime Minister interview with Karl Stefanovic and Allison Langdon

Karl Stefanovic: PM, good morning to you. Do you have blood on your hands?   PRIME MINISTER: No, it's obviously absurd. What we're doing here is we've got a temporary pause in place because we'v...

Karl Stefanovic and Allison Langdon - avatar Karl Stefanovic and Allison Langdon

Prime Minister Scott Morrison delivered Keynote Address at AFR Business Summit

Well, thank you all for the opportunity to come and be with you here today. Can I also acknowledge the Gadigal people, the Eora Nation, the elders past and present and future. Can I also acknowled...

Scott Morrison - avatar Scott Morrison

Morrison Government commits record $9B to social security safety net

The Morrison Government is enhancing our social security safety net by increasing support for unemployed Australians while strengthening their obligations to search for work.   From March the ...

Scott Morrison - avatar Scott Morrison

Business News

Victorian businesses can claim a rebate on COVID-19 deep cleans until 30 June - but many remain unaware

With exposure sites on the rise and financial stresses already on most Victorian businesses, the recent Business Victoria announcement of a substantial 80% COVIDSafe Deep cleaning rebate is a time...

Article by Damien Smith, CEO of Prime Group - avatar Article by Damien Smith, CEO of Prime Group

Six Tips to Get your Business Known on Social Media

Social media is one of the most effective ways to market your brand to the masses. With the meteoric rise in popularity of various social media platforms over the past decade, millions of brands h...

NewsServices.com - avatar NewsServices.com

Boom in Aussies buying up restaurants, pubs, hotels and bars in regional centres

With international borders closed, regional Australia is seeing a dramatic surge in popularity as people move out of the cities and into their quaint communities. City slickers are looking for new...

Tess Sanders Lazarus - avatar Tess Sanders Lazarus