Guide to the Contraceptive Pill

Reviewed by

Team Kin

⚡️In a Nutshell

  • Oral contraceptive, otherwise known as “The Pill”, is 99% effective when used correctly.
  • There are two types of birth control pill: the combination pill, which uses a mix of synthetic forms of estrogen and progesterone (called progestin), and the mini pill, which is progestin only.
  • While both mild and serious side effects can occur, taking a careful inventory of your medical history, doing the research on the different pills, and paying careful attention to your body when you start taking the pill will allow you to find the pill that best works with your body and eliminate many side effects.
  • The pill can help regulate your period and ease symptoms of PCOS, endometriosis and other serious menstrual conditions.
  • Ultimately, the pill can make your monthly cycle more stress-free, even allowing you to skip your period.

☝🏼 What is ‘The Pill’?

Women owe a lot to Margaret Sanger, the pioneer of women’s reproductive rights and founder of the American Birth Control League, the precursor to Planned Parenthood. It was her life’s work to fight for women’s reproductive rights and family-planning support.

In 1951, she convinced Dr Gregory Pincus to develop the first oral contraceptive and run the necessary clinical trials. In 1960, the pill was officially approved by the Food and Drug Association (FDA).

The Pill quickly began making its way through the Western world, landing on Australian shores in 1961.

To be the only medication in history to universally be known simply as "The Pill" is no small feat. Oral contraceptive is still considered one of the biggest medical breakthroughs of the 20th century.

However, until 1972, freedom came with a hefty 27.5% luxury tax and was only available to the married ladies. Thankfully, that’s no longer the case, with around 27-34% of Australian women claiming the pill as their go-to for contraception.

There’s a lot more to The Pill than simply knowing that it’s 99% effective at preventing unwanted pregnancy (when used correctly), and to be honest, there are plenty more reasons that taking it can be beneficial.

But first things first.

🙇🏼‍♀️ How Does the Pill Work?

The short answer is that it stops you from ovulating. If you don’t ovulate, there’s no mature egg released. Simply put, no egg = no chance to get pregnant.

The pill works by synthetically keeping the levels of estrogen and progesterone equal at all times.

This stops the pituitary gland in your brain from sending signals that release the two hormones that trigger ovulation, Follicle Stimulating Hormone, which signals the growth and maturation of ovarian follicles, and Luteinizing Hormone, which prepares a mature egg follicle to burst and release the egg.

In addition to this, the pill also helps prevent pregnancy by changing the consistency of your cervical mucus, making it harder for sperm to get through.

To break it down even further, there are two versions of the pill to choose from, and they work in different ways.

💊 The Combined Pill

This is the OG birth control pill and the one that most people are referring to when talking about “the pill”. It’s made using a combination of estrogen and progestin, which works to prevent pregnancy in three ways.

Firstly, by preventing ovulation, as detailed above. Remember, no egg, no chance of pregnancy.

Secondly, it thins the lining of your uterus, essentially making it a hostile environment incapable of nurturing a fertilised egg (if one were to exist). Sounds harsh, but we promise no eggs were harmed in the thinning of this uterine lining.

Lastly, this combination of hormones thickens your cervical mucus, creating an ironclad barrier between your uterus and sperm.

Okay, maybe it’s not ironclad, but it makes it nearly impossible for the little swimmers to pass your cervix.

Three powerful forms of protection, one itty bitty pill.

What’s with the Bleeding Then?

The reason you still get your period when on birth control is because the sugar pills in your pack don’t contain any hormones, which triggers the body to release the uterine wall, even when one hasn’t really been built up. It’s essentially “withdrawal bleeding” from the reduction in hormones.

The good news is that a thinner uterine wall means lighter, shorter periods. Amen to that, sis.

💅 The Mini Pill

The mini pill contains progestin only and is great for women for whom it may not be ideal to be exposed to additional estrogen.

It’s also commonly prescribed for breast-feeding mothers, as some studies have shown that estrogen can interfere with the lactation process.

Progestin is a synthetic form of the hormone progesterone, which is produced after ovulation by the corpus luteum (the discarded follicle sac of your mature egg) in a regularly ovulating body. It’s purpose is to support the development of the endometrium (uterine wall) to make it suitable to host a fertilised egg (aka embryo).

However, when the hormone is present at high levels, it not only prevents the body from ovulating, it actually regulates the uterine wall, preventing it from getting too thick.

A growing egg needs a nice, thick, cushy uterine wall to grow in. So, no chances of implantation here.

The other thing to note is that the mini pill consists of only active pills, meaning there are no placebo pills in the pack. While technically this means there will generally be an absence of the actual period, the lack of estrogen can still allow for some breakthrough bleeding to occur, especially if you miss a pill - even by a few hours.

🤔 So, I Can Skip My Period?

One of the major draw-cards of taking birth control is the ability to forego that monthly ritual of letting it flow, which can, let’s be honest, feel a little like being a part of a sacrificial ceremony at times.

But is it safe to skip your period?

In short, yes. But the truth is, it really depends on your individual body.

There are heaps of reasons you may want to skip your period, which range from serious medical conditions like endometriosis and dysmenorrhea, to more practical reasons, like the beach holiday you’ve planned.

For many women, like active-duty military, who work in environments with limited access to clean bathrooms, the ability to control menstruation at work is not just convenient, it’s often necessary.

Severe menstrual symptoms like excruciating pain caused by endometriosis, intense mood disorders caused by PMDD, and menstrual migraines don’t get activated when you skip your period, so the benefits can reach far beyond convenience.

To Skip or Not to Skip?

The effectivity rates of birth control drop to about 91% when factoring in human error, like inconsistency in the time of day you take The Pill. But let’s be real here, we’re all human. Other than the obvious reassurance that monthly bleeding does, in fact, confirm that you are not pregnant, there are a few other reasons that you may choose not to skip.

The process of menstruation and actually getting your period is a sign that your body is functioning properly, and if you suddenly stop, it could signal that there are other issues at hand that should be investigated with your GP.

Let’s Review the Benefits

Outside of safeguarding you against unwanted pregnancy (which let’s be honest, is huge), The Pill can regulate your body’s naturally occurring hormones, helping with all kinds of symptoms caused by imbalances, including acne, severe PMS, menstrual cramps, and irregular periods.

The Pill also helps reduce the symptoms of endometriosis and polycystic ovarian syndrome (PCOS).

🧠 The Pill, PCOS & Endometriosis

There are some major benefits to taking The Pill, particularly for women who suffer from endometriosis, polycystic ovarian syndrome (PCOS), and their side effects.

It’s estimated that around 10% of women suffer from endometriosis or PCOS, and while it’s not exactly clear what causes these issues, they’re categorised by unbearable pelvic pain, irregular cycles and things like acne or hair in unusual places. So knowing there is some relief, is... well... a relief.

Endometriosis is the overproduction of the uterine lining, causing it to grow on other areas of the body, such as the ovaries, bowel, rectum, bladder, and around the pelvis. PCOS is the growth of numerous small or large cysts along the outer edge of the ovaries.

The Pill regulates hormone levels in the body and stops the uterine wall from building up excessively (called endometrial hyperplasia), as well as preventing the development of ovarian cysts, essentially keeping these two at bay.

While the oral contraceptive has been shown to improve symptoms, it shouldn’t be considered a one-size-fits-all solution. As always, it will depend on your individual body and needs. It’s always best to discuss your options with your doctor.

🤦‍♀️ What Messes with The Pill?

Yea, she’s tough, but there are still a few watch-outs when it comes to the effectiveness of your pill.


Some medications can reduce The Pill’s effectiveness by increasing the metabolisation of hormones.

Specifically, one study showed that consistent use of antibiotics such as rifampicin and rifabutin, drugs used to treat tuberculosis and meningitis, and a selection of anticonvulsants can prevent the pill from suppressing ovulation.

These drugs increase enzymes in your body, which can interfere with the processes of oral contraception. Others include:

• anti-fungal drugs

• certain drugs used to prevent seizures

• HIV medications

Even though the research on the interference of these medications with birth control is limited, it’s best to exercise caution if you’re taking anything that may put you at risk. Use a back-up method of birth control throughout the course of your treatment and for at least one week after.


Most supplements have no effect on contraception, but a select few herbs, extracts, and other natural supplements can make contraception less effective by decreasing absorption or interfering with the breakdown of the hormones. This has been particularly shown in studies of women taking St. John’s Wort and oral contraceptives.

The below listed supplements have also raised concerns of causing interference with The Pill. If you’re taking any of the below or additional herbal supplements, be sure to read the packaging carefully and speak to your pharmacist about the potential impact it may have on the effectiveness of your pill. Always use a backup form of contraception if you’re unsure.

• Flaxseed

• Saw Palmetto

• Garlic pills

• Alfalfa

• St. John's Wort

All of these supplements are best avoided if you use The Pill as your only form of birth control. If you accidentally take any of the supplements listed above, it’s best to use condoms or another secondary form of birth control to reduce your risk of pregnancy.

Digestive Disorders

Your body needs to fully absorb each and every birth control pill you take in order to stop you from becoming pregnant. If you have a digestive or autoimmune disorder like Crohn’s disease, Celiac disease, or IBS, it could make the pill less effective.

Temporary digestive issues such as vomiting or diarrhea also have the potential to make The Pill less effective, so it’s important to use a second form of birth control, such as condoms, if you experience acute diarrhea that lasts for longer than 24 hours at a time.


If your BMI places you in the overweight or obese range, you have a higher risk of becoming pregnant while using contraception than women who BMI is lower.

In a 2015 study, researchers found that women with a BMI of 27.3 or higher had a 60% higher risk of becoming pregnant while using the birth control pill than women with a BMI that ranked in the mildly overweight category or lower.

Women with a BMI higher than 32.2 have a more than 100% higher risk of becoming pregnant while using contraception.

In general, the effectiveness of contraception decreases as your weight and BMI increases.

😯 Missed a Pill?

It’s important to take your pill at the same time every day for the best results and effectiveness.

For some, that means taking it first thing in the morning, or setting an alarm reminder at the same time every day.

But, life gets in the way.

If you miss a pill, take it as soon as possible (even if this means taking two pills on the same day). If you miss more than one pill, take the missed pill as soon as you remember, but ensure you’re using a back-up form of contraception until you’ve taken seven hormonal pills in a row.

Always refer to the instructions on the packaging of your specific pill to ensure you’re following the best procedure and are protected.

Just a note: if you miss a sugar pill, then there’s no need for concern.

In fact, some packs don’t even have sugar pills. Sugar pills contain no hormones and serve the purpose of only keeping you in the habit of taking the daily pill and keeping you on track when it comes time to start a new pack of hormonal pills.

Attention Mini Pill Users

The above advice does not apply.

If you’re taking the mini pill, your contraception has lower levels of hormones, meaning if you miss a mini pill by even three hours it may reduce the effectiveness.

It’s absolutely necessary to use a backup form of contraception for at least two days if you miss one of your mini pills.

🧐Common Side Effects

There are a range of potential side effects that come with The Pill. For the most part, they aren’t incredibly serious and should subside after your body adjusts, usually within one month.

Breakthrough Bleeding

Some women experience bleeding during their cycle if they choose low dose pills or mini pills.

Similarly to what happens when taking the sugar pills in your pack, the lower dosage or lack of estrogen can trigger the body to release the uterine wall and cause spotting.

Weight Gain

Perhaps one of the most common concerns when making the decision to go on the pill is weight gain. It’s not unheard of to pack on five kilos during your period, and lose it just as quickly. Well, almost as quickly, depending on how much chocolate you ate while binging Netflix under a heated blanket.

The key to that sentence is “lose it just as quickly.”

The truth is, there is actually no link between weight gain and oral contraceptive. What there is, however, is a link between increased levels of estrogen and fluid retention. Tricky, eh?

Medically, this is known as premenstrual fluid retention and it occurs naturally in your cycle as hormones fluctuate and estrogen and progesterone levels rise.

When taking the combined pill, estrogen levels can be anywhere from 6 to 10 times higher than normal, so naturally, fluid retention can be triggered.

If you notice a rapid increase on the scale within the first few weeks of taking the pill, without any major changes to diet and exercise, it’s most likely fluid rather than fat. As you maintain your normal health habits, you’ll notice your body will adjust and you’ll gradually make your way back toward the norm.

Breast Tenderness

Again, similarly to what happens naturally during your cycle when your hormone levels increase, The Pill can stimulate breast tissue, resulting in anything from mild discomfort to enlarged breasts.

While The Pill can cause benign lumps to occur in your breasts, studies have actually shown a decrease in hospitalisation for the treatment of these non-cancerous growths amongst women who take the pill.

However, know your boobs, ladies! Keep tabs on anything that feels out of the ordinary and when in doubt, see your doc.


While it may occur when you first start taking the pill, nausea is more commonly a result of emergency contraceptive use than regular birth control.

Lower Sex Drive

Because The Pill reduces the levels of androgens in your system, it can unfortunately have the adverse effect of lowering your sex drive, with about 15% of women reporting changes to their libido.

Testosterone is the major androgen associated with our sexual urges, and our bodies naturally ups its production during ovulation to encourage frisky business at prime fertilisation time.

We’re not only not ovulating when taking The Pill, but the increased levels of female sex hormones hinder the production of testosterone. You get the picture.

Less Common, More Serious

There are some less common, albeit more serious, side effects involved with the pill. Similarly to the above, the majority should subside, however, if any of the symptoms listed in this article persist or really strike you as out of the ordinary, speak to your doctor ASAP.

Headaches & Migraines

Increased risk of headaches and migraines is more common in users of the combined pill, so if you’re already susceptible, choosing the mini pill or a lower dose combined pill may be best.

Migraine headaches affect 37% of women of reproductive age and to be honest, can be completely debilitating.

Migraines are characterised by severe pain and throbbing, and can be accompanied by nausea, vomiting, and extreme sensitivity to light. They last from hours to days.

If you begin suffering migraines after starting birth control, speak to your doctor immediately, as it may signal an increased risk of stroke and it’s best to seek an alternative option.

Mood Changes

Truthfully, the links between oral contraceptives and mood changes are understudied.

However, one particularly oft-cited study in Denmark has shown links between increased hormone levels (particularly progesterone) and depression. This is also why during a normal cycle you experience symptoms of PMS when progesterone levels are on the rise.

Keeping in mind your levels are elevated continuously whilst using contraceptives, there is a slightly higher chance to experience feelings of depression, anxiety or fear, with about four to 10% of women reporting negative changes to their mood.


While some studies show a link between breast cancer and birth control pills, they also show that risk increases slightly in women who use the pill for more than five years. However, the risk is ultimately small, increasing from about one times higher to 1.6 times higher.

That said, thanks to The Pill’s regulation of the development of the uterine wall, taking The Pill has actually shown a 50% reduction in risk of endometrial cancers, a reduced risk of developing ovarian cancer, and an almost complete cessation in the development of ovarian cysts.

That’s pretty fab news.

Blood Clots and Deep Vein Thrombosis (DVT)

The FDA (Food and Drug Association) has reviewed a selection of studies identifying an increased risk of developing blood clots, including DVT, in women taking birth control pills containing progestin. The FDA found the risk at about three to five times higher than the average healthy, non-pregnant, non-birth-control-taking woman.

That may sound pretty scary, but to put this into perspective, the risk of developing blood clots during pregnancy is five to 20 times higher than the average woman, and even more so in postpartum.

While estrogen has been linked to an increase in blood clots, the risk is actually considerably low assuming you’re not predisposed to their development. If you are, it’s extremely important to have a conversation with your doctor about the best possible contraceptive solution for you.

You may be predisposed to blood clots if you’ve had surgery, trauma to the body or brain, pregnancy, hormonal therapy or are immobile.

Blood clots can also be genetic, so getting a good grasp on your family health history is important. If you have previously had any blood clots, or are aware of any family history of blood clots, it’s extremely important this is brought up with your doctor. It may not be appropriate for you to be on the combined pill and alternative options should be discussed.

🤨 Does the Pill Decrease Fertility?

This is a big one, as there is a lot of speculation around the fertility rates of long-time hormonal birth control users.

In short, years of taking the pill won’t affect your long-term fertility in itself.

In fact, a study out of UPenn showed 81% of subjects achieving pregnancy within a year of stopping the pills.

In some women, their menstrual cycle may take some time to return to normal after stopping the pill. If your cycle hasn’t returned after three months, speak with your doctor.

However, there are a number of other factors that can affect your fertility rates, so even while you’re adamantly preventing pregnancy in your early years, be sure you’re staying on top of your overall fertility knowledge if you do want kids one day.

Feeling Ready?

That’s a whole lot of information, but all up, it’s super important to know the facts before you jump in, and that goes for just about anything.

Every body is completely unique and there’s no one-size-fits all solution. Assess what’s most important to you in terms of your contraceptive choices and speak to your doctor or get in touch with one of our Kin GPs. We can help you make a choice that’s right for you.


  1. Claringbold, L., et al. Factors influencing you women’s contraceptive choices. Australian Journal of General Practice, 2019.
  2. Stachenfeld, Nina S. Sex hormone effects on body fluid regulation. Exercise and sport sciences reviews, 2008.
  3. Gallo, MF., et al. Effect of birth control pills and patches on weight gain. Cochrane Review, 2014.
  4. Mishell, DR Jr., Noncontraceptive health benefits of oral steroidal contraceptives. American Journal of Obstetrics and Gynecology, 1982.
  5. Nuttall, Frank Q. Body Mass Index: Obesity, BMI, and Health: A Critical Review. Nutrition Today, 2015.
  6. Vessey, M., et al. Oral contraceptives and benign breast disease: an update of findings in a large cohort. Contraception Journal, 2007.
  7. Skovlund, CW., et al. Association of Hormonal Contraception with Depression. JAMA Psychiatry, 2016.
  8. Gingell, M., et al., Oral contraceptive use changes brain activity and mood in women with previous negative affect on the pill. Science Direct, Psychoneuroendocrinology, 2013.
  9. Zimmerman, Y., et al. The effect of combined oral contraception on testosterone levels in healthy women: a systematic review and meta-analysis. Human reproduction update, 2014.
  10. Pastor, Z., et al. The influence of combined oral contraceptives on female sexual desire. The European Journal of Contraception and Reproductive Healthcare, 2013.
  11. Morch, LS., et al. Contemporary Hormonal Contraception and the Risk of Breast Cancer. The New England Journal of Medicine, 2017.
  12. de Melo, AS., et al. Hormonal contraception in women with polycystic ovary syndrome: choices, challenges, and non-contraceptive benefits. Open access journal of contraception, 2017.
  13. FDA Drug Safety Communication: Updated information about the risk of blood clots in women taking birth control pills containing drosperenone, 2012.
  14. Zhanel, G., et al. Antibiotic and oral contraceptive drug interactions: is there a need for concern? The Canadian Journal for Infectious Disease, 1999.
  15. D’Arcy, PF., Drug interactions with oral contraceptives. Drug Intelligence and Clinical Pharmacy,1986.
  16. Hitchcock, C., et al. Return to fertility after cessation of a continuous oral contraceptive, 2008.
  17. Davis, AR., et al. Occurrence of menses or pregnancy after cessation of a continuous oral contraceptive, 2008.
  18. World Health Organisation: Selected practice recommendations for contraceptive use, 2016.