Four ways women can fall pregnant while using the Pill — and how to reduce the risk.

November 6, 2016

Image: Knocked Up.

Last week, the news that detox teas could interfere with the contraceptive Pill — and potentially result in an unplanned pregnancy — came as a shock to many of us.

It was an all-too-real reminder that falling pregnant while taking the Pill can happen, although thankfully it’s relatively uncommon. According to Family Planning NSW, the combined Pill is 99.7 per cent accurate with perfect use — perfect being the operative word here.

When you’re a woman living in The Real World and not a scientific lab, it’s likely your Pill-taking behaviour is a little less than perfect. You might accidentally run out of pills, or experience vomiting or severe diarrhoea during your cycle. These things happen, and they’re considered part of ‘typical’ or ‘real world’ Pill usage.

The combined Pill is 99.7% accurate with 'perfect' use.

With 'typical use', effectiveness drops back to around 91-92 per cent. It's a case of 'be alert (and educated) but not alarmed' — there are a number of factors that can impact on the efficacy of oral contraception, so here's a quick refresher.

1. Inconsistency

According to Associate Professor Stephen Robson, Vice President of The Royal Australian and New Zealand College of Obstetricians and Gynaecologists, the biggest risk factor with the Pill is simply forgetting to take it every day.

"The combined pill works by stopping the release of eggs. For the combined pill to be effective it has to be taken regularly, and to be absorbed properly... Missing as few as two pills in a row, particularly just before or just after the period, can potentially lead to unexpected pregnancy," Associate Professor Robson explains. With the mini Pill, which needs to be taken more precisely, missing just one day could put you at risk.

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If you miss two combined pills, take them as soon as you realise and continue your packet, but use a second form of contraception until you've taken at least seven active pills in a row. Moreover, if you take the placebo 'sugar' pills — some women opt to skip them so as not to experience bleeding — it's also imperative you return to taking the active pills again afterwards when those seven days are up to ensure you remain protected.

"Women who (like me!) are very forgetful might wish to discuss using what we call a LARC - a long-active reversible contraceptive such as an IUD or a rod - so they don't have to remember," Associate Professor Robson suggests. (Post continues after gallery.)

Unplanned pregnancies on the big screen

Juno

Orange is the New Black

Love, Rosie

Twilight

Sex and the City

Unexpected

Knocked Up

Waitress

2. Some medications and supplements

Using certain additional medications while on the Pill can affect its absorption and thus stop it from working properly. It's important to talk to your doctor or healthcare provider about any medications you use while taking hormonal contraception.

"People who take medications that make the liver work harder — such as some medications that are used to treat epilepsy — might need to take a higher dose," says Associate Professor Robson.

The mechanism of the combined Pill can also be affected by St John's Wort, which is often used to treat depression. Researchers say the herbal remedy can speed up the body's metabolism of the oestrogen in combined Pills, thus affecting its levels.

3. Travel

Always remember to pack your Pill.

Overseas holidays are a lot of fun, but they can potentially affect how consistently you take the Pill. Long-haul flights that cross timezones can mess with your schedule — the Travel Doctor website recommends taking your pill at the usual time (i.e. "home time") while in transit, then gradually adjusting to a local time that works for you when you've settled in your new time zone.

Also be mindful that severe diarrhoea and vomiting — something that's not uncommon when you're travelling — can render the Pill ineffective - which brings us to our next point.

4. Vomiting and diarrhoea

"There are always concerns when women have an illness that causes vomiting that they may not absorb the Pill, making it ineffective," Associate Professor Robson explains.

Diarrhoea can also cause issues with absorption of the Pill. This is where the issue arose with detox teas — 'colon cleanse' teas in particular tend to have a laxative effect. If you do experience diarrhoea while using the Pill, particularly within hours of taking your tablet, Family Planning NSW recommends following instructions for missed pills — just in case.

Do you use the Pill? How do you ensure you take it consistently?

Popular forms of birth control

CondomsThe male condom is a barrier contraception that prevents both pregnancy and the transmission of STDs. They work by collecting semen so it doesn't enter theman's partner's body. Condoms are 95 to 99% effective at preventing pregnancy.

Contraceptive pillThe Pillis the most popular form of birth control. There are two types: the combined pill, containing two hormones, and theprogestogen-only, or mini, pill, which only contains one female hormone. The combined pill works by preventing the ovary from releasing an egg each month. The mini pill changes the mucus at the entrance of the uterus, which stops sperm from entering. Both are 99.7% effective; however, they don't offer protection from STDs.

Intrauterine deviceIUDs are small, T-shaped devices that are inserted into the uterus by a doctor in order to prevent pregnancy. There are two types of IUD: copper, which affects the movement and survival of sperm in the womb while changing the lining of the womb;and hormonal, which releases progestogen (a synthetic version of the naturally-occurring hormone progesterone) into the uterus. Although IUDs have a success rate of more than 99%, only around 2% of Australian women currently use one.

The female condomThe female condom is a pre-lubricated sheath, which loosely fits inside of the vagina. The condom has a removable ring, which helps to insert the sheath and keep the condom in place. A larger ring remains on the outside to cover the opening of the vagina. They are designed to fit all women and can only to be used once. Due to misuse of the product it is only 79 per cent effective.

DiaphragmLike the male condom, the diaphragm is a barrier method of contraception. It's a shallow silicone dome that's inserted into the vagina andcovers the cervix, which is the entrance to the uterus. It's held in place by the pelvic muscles, and works by preventing sperm from entering the uterus. After sex, diaphragms need to remain in placefor another six hours, in which time the sperm inside the vagina die. This method is 88 to 94% effective at preventing pregnancy, although this rate increases with experience.

Birth control implantThis is a 4cm-longimplant that is inserted into a woman's upper arm, just under the skin, by a doctor. It releases a hormone called etonogestrel, which prevents ovulation and thickens the mucus in the cervix, which can stop sperm from entering. Contraceptive implants - usually sold as Implanon - are removed under anaesthetic every three years, and are close to 100% effective.

Vaginal ringVaginal rings are soft plastic rings that contain the same two hormones as the combined pill - oestrogen and progestogen. The ring is inserted into the vagina, where the hormones are absorbed into the body and then prevent the ovaries from releasing eggs. Once inside the ring can't be felt, and it needs replacing every three weeks (with one week's break in between). When used correctly, this method is more than 99% effective.

Depo ProveraDepo is a long lasting hormonal injection. The synthetic form of progesterone is administered every 12 to 14 weeks to woman, preventing pregnancy within this ongoing time period. The injection, which is given in the buttock or muscle of the upper arm, prevents ovulation and thickens the mucus in the cervix, helping to block sperm. The injections are 99 per cent effective but do not protect against STDs. Male contraceptive injections are currently being trialled

The morning after pillEmergency contraception (popularly referred to as the morning after pill) is used to prevent a pregnancy following unprotected sex. Other reasons include missing a contraceptive pill or a condom breaking. It is common in Australia to use the progestogen-only method. This entails a dosage of EC pills containing progestogen or the synthetic version. A doctor can prescribe the pill or they can be bought over the counter at a pharmacy without a prescription. Emergency contraceptionis 85 per cent effective in reducing the risk of pregnancy.

SterilisationSterilisation is a permanent form of contraception. For women there are two types of sterilisation: tubal ligation, in which clips are placed on the fallopian tubes, or tubal occlusion in which a device is inserted into the tubes. These methods work by preventing the sperm from reaching the egg. Tubal litigation is 99.5 per cent effective. The Vasectomy (for men) works by cutting and blocking the tubes called the vas deferens, preventing sperm from leaving the testicles. The chances of impregnation with a vasectomy are 1 in 1000.

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