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Did you know?
Common questions about contraception
Why use contraception?
Women who choose not to use any birth control and who are sexually active for one year have an 85% chance of becoming pregnant in that year (depending on variables such as age and frequency of intercourse).1 Worldwide, more than a quarter of women who become pregnant have either an abortion or an unplanned pregnancy.2 The use of contraception, or birth control, can significantly lower your chances of becoming pregnant unintentionally.
People choose to use contraception for a variety of reasons:
- You may have decided that you don’t wish to have children or would love them – just at a later point in your life.
- You may choose to use birth control to help space the timing of the births of your children.
- You may be feeling like your family is complete, so you wish to guard against the possibility of becoming pregnant again.
Choosing the birth control that is right for you is a personal decision and should be an informed one. We are all individuals and have our own unique needs, so we may prefer a particular contraceptive method over another – depending on our health, sexual, moral, or reproductive needs.
Are there certain times when you need to be more careful?
An egg is only available for fertilization for about a 12-24 hour window each month – this is known as ovulation. A woman is more likely to get pregnant during the five days leading up to ovulation and the one day after it. This is because sperm can live inside the female body for up to five days, so even if a woman does not ovulate for another four days after having sex, there could still be sperm living inside of her that can fertilize the egg when it is released. Therefore if a couple is having unprotected intercourse and doesn’t wish to become pregnant, they should avoid intercourse during this time. People try to avoid pregnancy by figuring out when they are most fertile, known as a “natural” method of family planning. It is important to note that this is a relatively unreliable method of family planning. Timing ovulation can be tricky as it may not always happen at the same time each month.
How do I compare the effectiveness of different contraceptive methods?
Some contraceptive methods are more reliable than others, and your contraceptive method of choice impacts your ability to avoid an unintended pregnancy.
The Pearl Index is the most common technique used in clinical trials for measuring the effectiveness of a birth control method, and is named after Raymond Pearl, who introduced it in 1933. Usually two different Pearl Indices are published from studies of birth control methods:
- Typical use, which refers to failure rates for people who do not consistently or always correctly use their birth control
- Perfect use, which refers to failure rates for those whose use is consistent and always correct.
Types of contraception »
What leads to contraception failure?
Some contraceptive methods are more prone to failure than others. There are various reasons for contraception failure, usually caused by incorrect use or misunderstanding about use, therefore it is important to understand how your chosen method works and how you need to use it – if in doubt, ask a healthcare professional.
Common myths about pregnancy »
Did you know?
Common questions about barrier methods
Condoms
Are condoms effective against HIV and other STIs?
Yes, but only if they are used properly.
How are condoms tested?
There are a range of tests performed by both regulatory agencies and the condom manufacturers. These include electronic testing, the water leak test, the air burst test and the strength test.
How can I check a condom is safe to use?
Check that the use-by date has not expired, that they carry a standards approval mark (either FDA, ISO, CE or the British Standard Kite Mark), and that they have been properly stored.
How often do condoms fail?
Studies have shown that when condoms are used correctly, they are 93% effective (70 women in every 1,000 will get pregnant per year)3-8
If female condoms are used properly, they are 95% effective (50 women in every 1,000 will get pregnant per year)9
How much protection do condoms give against pregnancy? If a condom breaks what are the risks of pregnancy?
When used properly (i.e. the condom doesn't split or burst), they can be very effective in preventing both pregnancy and STIs. If a condom breaks and no other form of contraception such as the contraceptive pill is used, then there is a risk that a woman may become pregnant, so you should consider using emergency contraception. There is also a risk of contracting a STI.
Is it possible to get different sizes of condoms?
Condoms are made in different lengths and widths, and different manufacturers produce varying sizes. There is no standard length for condoms, though those made from natural rubber will in addition always stretch if necessary to fit the length of the man's erect penis.
The width of a condom can also vary. Some condoms have a slightly smaller width to give a ''closer'' fit, whereas others will be slightly larger.
Is using two condoms better than one in avoiding pregnancy?
Using two condoms at the same time-either two male condoms or a male and female condom- is not a good idea as the friction may result in one or both of the condoms tearing. If you want to take extra precautions against pregnancy when having sex, and are concerned about the possibility of a condom breaking it is better to use another form of contraception. For example, using a contraceptive pill as well as a condom will ensure that you both have double protection against pregnancy as well as protection against STIs.
Can you use a condom under water?
you are going to use a condom under water it is important that you put the condom on before you get into the water. Also, if the water contains chemicals such as chlorine, or additives such as soap, bath oil or bubble bath then this may affect the latex.
Where can I get condoms?
You can get condoms from chemists, supermarkets and your local family planning clinic.
Does using a male or female condom make sex less pleasurable?
Some people find that condoms interfere with spontaneity and sensation, but they can be fun to use once you have got used to how they need to be put on.
Are female condoms harder to use than male condoms?
As with most barrier methods, it can take a bit of practice to use this method correctly. As long as you are clear on how to use them, you should get the hang of it.
If I use a female condom, will there be a lot of mess?
Female condoms work in a similar way to the male condom, the sheath works by containing the sperm when the man ejaculates. They are therefore not messy to use if used correctly.
Diaphragm and cervical cap plus spermicide
What happens if I accidentally swallow some spermicide?
Most spermicides have an unpleasant taste but will not usually harm you or make you feel ill, however it is advisable to avoid swallowing excessive amounts. If you are concerned about feeling ill following swallowing some spermicide, you should seek the advice of a healthcare professional.
How does a spermicide work?
Spermicides contain substances that kill sperm. Some products also form a thick foam or mucus which blocks the cervix and acts as a barrier against the sperm. They can come in the form of foam, foaming tablets, pessaries, creams, jellies and sponges. Spermicides are not effective enough when used alone, and should be used in combination with barrier methods such as the diaphragm or cap.
How is a diaphragm fitted?
A pelvic examination by either a physician or a skilled healthcare professional is required for fitting diaphragms. Fitting rings are produced by diaphragm manufacturers in various sizes and with different rim types. Sizes range from 50 to 105 mm. They are most commonly available in flat spring or coil spring rim types. Diaphragms between 60 -85 mm in diameter will provide the correct fit for most women. Initially the fitting ring size is estimated by clinical assessment of the vaginal length. Smaller or larger sizes are then inserted until the correct fit is achieved. It is important that each individual is fitted with the type of rim that she will ultimately use as the rim type can affect fit and ease of insertion. It should fit snugly into the upper half of the vagina. The user should practice insertion under supervision and placement should be inspected to ensure that the fitting ring is correctly positioned in the vagina. Fitting is best done when the bladder is not empty so that the user can test to ensure that urination is easily accomplished with the selected fitting ring in place. The diaphragm may require resizing following a full-term pregnancy, pelvic surgery, or abortion, or if there is a major change in weight.
Can a diaphragm get lost or stuck inside my body?
There is no reason for the diaphragm to get lost or stuck inside your body. A diaphragm will be specifically fitted by a healthcare professional to ensure it fits and can be used effectively by you. If you are having a diaphragm fitted, you should practice insertion, placement and removal with the healthcare professional. The diaphragm should also be checked every six months by a healthcare professional to make sure it still fits properly.
Do I remove the diaphragm immediately after sex?
A diaphragm should be removed no sooner than 6 hours after intercourse and can be left in place for up to 24 hours after intercourse. Additional spermicide is required with subsequent acts of intercourse. If more spermicide is required it should be placed in the vagina and the diaphragm should be left in place.
What happens if I want to have sex spontaneously?
The diaphragm can be inserted immediately before or up to 6 hours before intercourse. Some people do find that this might interfere with spontaneity.
Did you know?
Common questions about hormonal methods
Pill
Are all pills the same?
No - there are many varieties of pill available today, and each of them is slightly different.
What does the pill contain?
There are two main types of pill. The pill can contain two types of hormone - an estrogen and a progestogen and some pills contain progestogen only. When you become pregnant the body produces these hormones naturally, to stop you producing any more eggs. The combined pill mimics this action, so that even though you are not pregnant, ovulation is prevented. It also thickens the mucus in the cervix, which makes it difficult for sperm to get through. The progestogen only pill works by thickening the mucus at the entrance to the womb. In some women it may also prevent ovulation.
Are there any side effects or health risks with the pill?
The pill has been safely used since the 1960s, and side effects are rare. Some women may have minor side effects when they first start taking the pill, but usually these subside after about 12 weeks. Side effects can include bleeding between periods, headaches and breast tenderness. Some brands of combined pill contain a higher dose of estrogen. If you are on this type of pill and are suffering from side effects, it might be helpful to ask your doctor if you can switch to a low-dose estrogen pill. There are also different types of progestogen available, so again, it is worth discussing the different options with your doctor. Different types suit different women.
Very rarely, a few women might suffer from thrombosis (blood clot). The risk of thrombosis depends on a number of factors, including family history, age and body weight, and increases if a combination of risk factors are present. The risk of thrombosis while on the pill is far less than the chance of developing thrombosis if you don’t use contraception and get pregnant.10 If you have ever suffered a blood clot, or you have a family history of thrombosis or circulatory disease, you should let your doctor know, as the pill may not be suitable for you.
You should also inform your doctor if you are a smoker, have diabetes or high blood pressure as these conditions also increase the risk of a clot, as do being very overweight or immobile (for example, wheelchair users).10
See your doctor at once if you develop any of the following symptoms:
- severe pain and swelling in the calf of one leg
- severe chest pain and difficulty breathing
- severe abdominal pain
- severe, prolonged headache - especially if you have not previously suffered from migraine
- loss of vision or weakness on one side of the body
- yellow eyes and skin (jaundice)
Although these symptoms are worrying, it must be stressed they are extremely rare and will not affect most women taking the pill.
There is an increased risk of developing breast cancer, but this is very small and returns to normal within ten years after stopping the pill.11 You need to balance this with the protection the pill gives against endometrial and ovarian cancer.10
Are there any additional health benefits to taking the pill?
Yes - as well as short-term benefits such as more regular, lighter and less painful periods, in the long-term the pill is known to reduce the risk of endometrial and ovarian cancer by as much as 20% and 50% respectively.10
How reliable is the pill?
The pill is one of the most reliable forms of contraception, giving a very high degree of protection against pregnancy when taken as instructed.
Are there any pills that offer extra benefits?
Some pills can improve the condition of your skin and hair, others help with symptoms such as acne, PMS, and cyclical bloating.
Should I take a break from the pill?
There is no evidence to suggest that the pill has any effect on long-term fertility or that it is necessary to take a 'pill break'.
What if I don't like the pill I'm on - can I switch?
Lots of different pills are available, and they are all slightly different. If you find the pill you are on does not suit you, there are plenty of others to choose from! However, usually it takes some months until your body is accustomed to a certain pill and too frequent changes would prevent you from finding any appropriate type. Talk to your doctor who will assist you.
Do I have to go to my doctor to be prescribed the pill?
Yes, your regular doctor can prescribe the pill for you.
How do I start taking the pill?
The most usual way is to start taking the pill on the first day of your period, this way you'll be protected straight away.
You can also start on days two to five of your period, although if you do this, you should also use another form of contraception (e.g. a condom) for the next seven days.
Do I take the pill every day?
The combined pill works across a 28 day cycle including the pill-free or placebo interval, which means you have one pack for each cycle. You take a hormonal pill every day for 21 days of the cycle, and then have a hormone free break of seven days where no pills are taken. During this break, you will still be protected and you will have a menstruation-like bleed. With the progestogen-only pill you have to take a hormonal pill everyday of the 28 day cycle.
Is it safe to have sex during the seven day pill free break?
Yes - as long as you have taken the previous pills as instructed. Also, if you do have sex during the pill free break (gap week) , it's important to start your next pack on time and make sure the pills are taken correctly.
Will my periods be affected?
The pill usually makes your periods more regular, shorter, lighter and less painful.
Do I need to take it at the same time every day?
Yes, morning or evening, it's up to you, but you do need to get into a regular routine of pill-taking. If you forget to take your pill, you'll still be protected if you can take it up to 12 hours later - but it's wise not to do this too often. Progestogen only pills can only be taken up to three hours late.
I missed a pill from my packet / I've vomited / I’ve had diarrhoea? What should I do?
I'm on antibiotics - how does this affect my pill?
Some antibiotics and other prescription drugs can reduce the effectiveness of the pill so always tell your doctor you're taking the pill if you are prescribed medicine.
How should I protect myself from STIs?
The pill does not offer protection against STIs (sexually transmitted infections), so, until you are sure of your partner's sexual history or sexual health, it's advisable to use a condom in addition to taking the pill.
Will the pill make me put on weight?
Although some women on the pill reported to having put on weight, it is very questionable that this could be traced back to the pill. However, with some pills you might put on weight when you start taking them, due to water retention, which makes you feel bigger. But there are modern pills which can avoid such water retention to some extent.
You may also find your appetite increases in the first three months of pill taking - and of course if you eat more you may gain weight!
Will the pill give me spots?
Actually some modern pills can help clear up your skin. Talk to your doctor about how the right pill could combat skin impurities or even acne. Sometimes women do break out in response to their pill, and if this is the case you should consult your doctor. With a number of different types of pill available today, you should be able to find the pill which is best for you.
Will the pill make me feel sick?
Some women do feel sick when they take the pill, but there are so many varieties available today - including modern, low-dose formulations - you should be able to find a pill to suit you.
Will I need to take a break from the pill after a few years to let my body recover?
There's no evidence or scientific rationale that this should be done. Doctors do recommend reviewing your contraceptive needs after around 15 years of pill-taking, or at the age of 35, but many women continue to take the pill until hitting the menopause.
Will long term pill use affect trying for a baby?
Large studies have investigated this and there is no evidence to suggest the pill has any long term effect on a woman’s ability to have a baby, even if it is taken for a long period of time.
Isn’t it going to be difficult to remember?
You should try to adopt a routine with your pill-taking to make it easier for you to remember.
Intrauterine system (IUS, also known as a hormonal coil)
Is it painful to have an IUS inserted?
An IUS insertion is usually well tolerated by most women. Local anesthesia may be applied to the uterine cervix prior to the insertion. Some women may experience pain and dizziness after insertion, which usually settles after resting for a short time.
What is the difference between an IUS and IUD?
The IUD is a small plastic T-shaped device covered by copper or other metals which is inserted in the cavity of the womb. The IUS, is made of two components: the plastic T-shaped device and a cylinder containing progestogen hormone, which is released slowly from the system. The IUS and IUD have a number of different characteristics and work in a different way, so the doctor and the patient need to find out together which option is more appropriate individually.
Can the IUS also be used as emergency contraception?
The IUS was not investigated for use as an emergency contraception.
Can the IUS come out or get stuck in my uterus?
The IUS must be inserted by a trained doctor, who will follow the necessary procedure to ensure it is correctly positioned. Occasionally, the muscular contractions of the womb during menstruation may sometimes push it out of place or expel it. Very rarely it can perforate the wall of the uterus. If a user of an IUS experiences any unusual bleeding, pain or discomfort, her doctor must be informed as soon as possible.
Will my partner or I feel it during sex?
Neither you nor your partner should feel the IUS during sexual intercourse. If you do, sexual intercourse should be avoided until your doctor has checked that the IUS is still in the correct position.
Is it safe to wear tampons during my period if I have an IUS fitted?
Use of sanitary pads is recommended. If tampons are used, you should change them more frequently, and with care so as not to pull the threads of the IUS when manipulating the tampon.
Will I bleed after having an IUS fitted?
The progestogen released from the IUS causes the lining of the uterus to become very thin. Therefore it can change your menstrual periods so that you can have shorter or longer periods, lighter or heavier bleeding, or no bleeding at all. When the IUS is first inserted, before the lining becomes completely thinned out, women may have unpredictable spotting (a small amount of blood loss). This usually clears after the first months following insertion. If it does not clear, then you should see your healthcare professional to make sure there is not another cause for the bleeding.
Will the hormones in the IUS affect my periods?
Many women with an IUS find that they experience an improvement of heavy and painful periods after the IUS is fitted. Some women may stop having their periods altogether.
Is it safe to have an IUS fitted for more than five years?
An IUS can be left in place for up to five years. After this time, it will need to be replaced with a new device. If this method of contraception has worked well for you, and if you still wish to use a long-term contraceptive option, then you can discuss with your healthcare professional about continuing with this method.
Intrauterine device (IUD, also known as the coil)
Is it painful to have an IUD inserted?
An IUD insertion is usually well tolerated by most women. Local anesthesia may be applied to the uterine cervix prior to the insertion. Some women may experience pain and dizziness after insertion, which usually settles after resting for a short time.
Can the IUD come out or get stuck in my uterus?
The IUD must be inserted by a trained doctor, who will follow the necessary procedure to ensure it is correctly positioned. Occasionally, the muscular contractions of the womb during menstruation may sometimes push it out of place or expel it. Very rarely it can perforate the wall of the uterus. If a user of an IUD experiences any unusual bleeding, pain or discomfort, her doctor must be informed as soon as possible.
Will my partner or I feel it during sex?
Neither you nor your partner should feel the IUD during sexual intercourse. If you do, sexual intercourse should be avoided until your doctor has checked that the IUD is still in the correct position.
Is it safe to wear tampons during my period if I have an IUD fitted?
Use of sanitary pads is recommended. If tampons are used, you should change them more frequently, and with care so as not to pull the threads of the IUD when manipulating the tampon.
Will I bleed after having an IUD fitted?
Women using an IUD are more likely to experience an increase in blood loss each month than non-users. This typically occurs because of increased duration and heaviness of menstrual flow, but may also result from irregular bleeding and spotting in between periods.
Will an IUD affect my periods?
Women with an IUD can experience an increased duration and heaviness of menstrual flow.
How long is it safe to have an IUD fitted for?
An IUD can be left in place from 3 up to 10 years, depending on the type. After this time, it will need to be replaced with a new device. If this method of contraception has worked well for you, and if you still wish to use a long-term contraceptive option, then you can discuss with your healthcare professional about continuing with this method.
Implant
Why does the implant have to be replaced after three years?
The implant contains a progestogen reservoir which is released in tiny doses during the three years to prevent pregnancy. It will need to be replaced after this time as the hormone reservoir will run out.
Can you feel it or see it from the outside?
The implant is about the size of a thin match, and people usually have it inserted under the skin of their left upper arm, not far above the elbow. It can easily be felt, but it is not very visible, except to someone who is looking for it. There will be a tiny mark at the point of insertion, but this isn’t very visible providing the implant has been inserted by a trained doctor.
Is it safe to have if you play a lot of sport or could exercise cause the implant to move out of position?
Migration of the implant is very rare, even with vigorous exercise, and is not known to be serious. If you cannot feel the implant where it was originally positioned, then speak to a healthcare professional to ensure it is located and repositioned if necessary.
Will the hormones affect my periods?
Many women find that heavy, painful periods are reduced. There can sometimes be irregular bleeding initially, but this should go after the first few months.
Is the implantation procedure painful?
Local anaesthetic is used so there should be very little pain, and the procedure takes only a couple of minutes. There might be a bit of bruising or soreness afterwards.
What if I don’t want it anymore, can it be easily removed?
Yes, the implant can be removed at any time, but this must be done by a trained healthcare professional.
Injection
Do I have to go to hospital for the injections?
The injections must be given by a healthcare professional. Depending on where you live, you can have the injection done at your local doctors or family planning clinic.
What if I miss an injection – will I get pregnant?
You do need to have the injection every three months. The amount of hormone which is injected to prevent unintended pregnancy will only last 12 weeks, so if you miss an injection you will not be protected against pregnancy.
How many injections can you have?
If you are sexually active and do not currently wish to have children, you can continue having the injections to protect against pregnancy, providing you find the method suits you and you have regular check-ups with your healthcare professional.
What if I want to have children, will the injection affect my long-term fertility?
Periods and fertility may take up to a year to return after stopping injections, and this may vary from woman to woman.
Does the injection cause you to gain weight?
Some women do experience weight gain, if this happens to you, speak with your healthcare professional, it may be that an alternative form of hormonal contraception is better suited to you.
Contraceptive Patch
If the patch falls off, will I have to use a new one, and will I become pregnant?
The patch is designed to adhere to the skin for a week, but if it does become detached you need to replace it as soon as possible as it will become ineffective as birth control if more than 24 hours pass. If more than 24 hours have passed between the patch falling off and it being replaced, then additional birth control will be required for one week.
Can the patch come off in the shower?
The patch is very adhesive and rarely comes off. You can go in the shower, swim and exercise whilst wearing. The patch should be applied to clean, dry skin and you should avoid using any creams or lotions near a patch you’re already wearing to ensure it sticks as much as possible.
The patch works by releasing the hormones estrogen and progestogen into the bloodstream.
The patch needs to be changed on the same day each week (the patch change day) with the fourth week being patch-free, which is when a period will occur. The patches need to be changed to ensure the right amount of hormones are released into the bloodstream, each patch can only release a certain amount. If you forget to change the patch for one or two days past the patch change day, remove the patch when you remember and apply a new patch. You will still change this patch on your next patch change day and you are still protected against pregnancy. If you are more than two days late changing the patch, you start a new four-week cycle with the new patch and will need to use a back up method of contraception, such as condoms, for the next seven days.
What happens if I forget to take off my patch at the start of my patch free week?
If you forget to take off your patch at the start of the patch free week, take it off when you remember and start the next cycle at the usual time. Your period may be shorter, or you may still be bleeding when you put on the next patch.
Do I have to wear the patch in the same place all the time?
No, it may actually help to change the location a bit each week. The patch can be worn on the buttocks, stomach, back or upper arms, it must not be worn on the breasts.
The patch just looks a bit like a plaster, how can I tell if the patch is working?
You cannot see any change in the patch, or feel it working, but it is continuously releasing the hormones estrogen and progestogen into the bloodstream. You just need to ensure you change the patch each week for three weeks, and remember to start the next cycle of patches after the fourth patch free week.
Vaginal Ring
What do I do if the ring falls out?
If the ring falls out, it should be rinsed off and replaced as soon as possible. If it has been out for less than three hours, you should still be protected against pregnancy. If it has been out for more than 3 hours, a back-up method of birth control is needed for the next seven days. The ring must stay in for at least 7 more days after being out for longer than 3 hours; this may mean that you wear it for more than 21 days in total that month. Following this, a one-week ring-free interval can occur and the next ring inserted.
What do I do if I forget to take the ring out?
If it has been in for less than 28 days then remove it, and have a seven-day ring-free interval, then insert the next ring. You are still protected against pregnancy. If the ring has been in for more than 28 days, remove it immediately, insert a new ring and use a back-up method of birth control for the next 7 days. You may have irregular bleeding, or no period that month.
What do I do if I forget to insert the ring after the week’s break?
Insert the ring as soon as you remember and use a back-up birth control method for 7 days. If you have unprotected sex after the ring has been out for more than one week, consider using emergency contraception. You should not have more than 7 days without wearing a ring a this puts you at risk of getting pregnant. Talk to your doctor if you are unsure.
Emergency Contraceptive Pill
How long after having unprotected sex can I take the emergency contraceptive pill?
The emergency contraceptive pill must be taken within 72 hours (three days) after unprotected sex. The sooner it is taken, the more effective it is.
Is it safe to use the emergency contraceptive pill more than once a month?
The emergency contraceptive pill should not be relied on as a regular form of contraception, as it is not as effective as other forms of hormonal contraception specifically made for regular use - it is only intended as a back-up. Due to the possibility of pregnancy, and changes of the menstrual cycle it is not recommended that the emergency contraceptive pill be used again before the next menstrual period.
Can I use the emergency pill with any other forms of contraception, e.g. if I have forgotten to take my contraceptive pill?
Yes, you can use the emergency contraceptive pill if something has gone wrong with your usual form of contraception, for example a forgotten pill or split condom.
- Trussell J. Contraceptive efficacy. In Hatcher RA, Trussell J, Stewart F, Nelson A, Cates W, Guest F, Kowal D. Contraceptive Technology; Eighteenth Revised Edition. New York NY: Ardent Media, 2004.
- The Alan Guttmacher Institute: Facts in Brief “Induced Abortion Worldwide”. 1999
- Leidenberger FA. Klinische Endokrinologie fur Frauenarzte. Berlin, Germany: Springer Verlag, 1998
- Baltzer J, Mickan H. Gynakologie: Ein kurzgefabtes Lehrbuch/Kern. Neuberbeitete Auflage. Stuttgart, Germany, Georg Thieme Verlag, 1985
- Organon. NuvaRing (etonogestrel/ethinyl estradiol vaginal ring) 2001. Available at: http://www.epigee.org/guide/inserts
/nuvaring.pdf. (Accessed 5 October 2003)
- Ortho-McNeil Pharmceutical Inc. Ortho Evra (Norelgestromin/ Ethinyl estradiol transdermal system) 2001. Available at: http://www.ortho.mcneil.com/products/pi
/pdfs/orthoevra.pdf. (Accessed 5 October 2003)
- Ortho-McNeil Pharmaceutical Inc. Ortho Tri-Cyclen Lo tablets (norgestimate/ethinyl estradiol) 2002. Available at: http://www.ortho-mcneil.com/products/pi
/pdfs/orthtricyclenlo.pdf (Accessed 5 October 2003)
- Speroff L, Darney PD. Periodic Abstinence. A clinical guide for contraception. 3rd edn. Philadelphia, PA: Lippincott Williams and Wilkins, 2001
- Trussell J. Contraceptive efficacy. In Hatcher RA, Trussell J, Stewart F, Cates W, Stewart GK, Kowal D, Guest F. Contraceptive Technology; Seventeenth Revised Edition. New York NY: Irvington Publishers, 1998
- Guillebaud, J. Contraception: Your Questions Answered. Churchill Livingstone, 2004.
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