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Medical School Hot Topic: Contraception
You should be aware of the various forms of contraception, and their different roles and mechanisms of action. A woman may choose from many options depending on reliability, ease of use, or how readily she is able to tolerate it - as well as her own personal preference.
Overview of Fertilisation and Pregnancy
Women can become pregnant when they are ovulating (i.e. after a mature egg cell has left the ovary). The egg passes along the fallopian tube, from where it enters the womb. Sperm cells must pass through the cervix and womb to the fallopian tube in order to fertilise the egg. Different contraceptives will therefore act to prevent this process in different ways - through preventing sperm reaching the womb, from preventing the embedding of fertilised cells, or influencing the hormones responsible for the cycle in order to prevent ovulation.
The most common hormonal methods (methods that prevent ovulation through the release of hormones) are as follows.
Birth control pills are taken on a 21 or 22 day cycle, and include oestrogen and progestin. The woman will have a period in the week in which she does not take the pill. Some women may choose to take the ‘mini-pill’ instead, which contains only progestin.
The contraceptive skin patch is placed on the body, and releases a combination of oestrogen and progestin. It is changed once a week and worn for the first three weeks of the cycle, and not worn in the fourth week.
Vaginal rings also contain a combination of hormones that enter the body through the vaginal wall. They are inserted and remain for 21 days, before being removed for the fourth week, in which the period occurs.
Hormone releasing contraceptive coils may be IUDs or IUSs (intrauterine devices or intrauterine systems) contain levonorgestrel, and must be inserted by a medical professional. The coil continuously releases hormone, preventing the implantation of fertilised eggs. The coil can remain in the womb for up to five years.
The possible advantages of hormonal methods are that they can stop excessive bleeding or period pain - disadvantages include sore breasts, headaches, nausea and thrombosis. There are also widely reported effects on mood.
Non-hormonal options have fewer side effects. However, they may be less reliable.
Female condoms are an internal condom covered with lubricant worn by the woman. They are as reliable as aa male condom, but are often found to be difficult or awkward to use.
Condoms prevent STIs as well as an unwanted pregnancy - however they are frequently misapplied, meaning that they can be highly unreliable.
Diaphragms are soft silicone cups which are inserted into the vagina, covering the cervix entirely. A spermicide is used in conjunction with the diaphragm, and the diaphragm is inserted into the vagina before having sex. It must be left there for at least six hours afterwards. They must be provided by a gynecologist.
The copper coil is a contraceptive inserted into the womb by a medical professional. The copper itself prevents the egg from being fertilised or embedding into the womb, through changing both the motility of the sperm and the mucus of the womb itself. There is also a ‘chain’ which works through a similar action, but lacks a frame. Both can be used for around five years, although may lead to pelvic infection or heavy periods.
Chemical contraceptive creams, gels, and suppositories are placed inside the vagina before sex. They create a barrier in front of the cervix, preventing the entry of sperm. They also normally contain spermicidal agents, meaning that they kill the sperm as well. However, they are unreliable and recommended only with other methods.
Natural birth control methods aren’t hugely reliable, and rely on the woman recording her body temperature and vaginal discharge, in conjunction with the timing of her normal period, to assess her fertility level.
Example Interview Questions
- What forms of birth control do you know about?
- Are there issues with common forms of birth control?
- Are any forms of birth control 100% reliable?
- How do hormonal methods of birth control work?
- How do non-hormonal methods of birth control work and can you name two different types?
- Can you name two of the hormones used in birth control products?
Interview Questions & Example Answers
What forms of birth control do you know about?
I would divide birth control forms into hormonal and non-hormonal. Hormonal methods include the birth control pill - containing oestrogen and progestogen - or the mini-pill which contains only progestogen. The contraceptive skin patch, hormone releasing contraceptive coils, the implant and vaginal rings are also all dependent on the release of hormones.
Non-hormonal methods include condoms, female condoms, diaphragms and contraceptive creams. Additionally, the copper coil is non-hormonal, relying on the copper itself to prevent fertilisation or embedding of the egg.
Are there issues with common forms of birth control?
Issues with some of the common forms of hormonal birth control include:
With the combined pill, mood swings, nausea, breast tenderness and headaches are all possible, and major side effects like blood clots and cervical cancer are possible but unlikely.
The implant will frequently lead to amenorrhoea (the stopping of periods whilst it is used).
The IUS may cause similar side effects to the pill.
The progestogen only pill may cause skin problems and breast tenderness.
Looking at non-hormonal methods, the IUD may cause heavy and/or painful periods for the first 3-6 months of use and carries with it a risk of infection.
All of the above do not protect against STIs.
Condoms protect against STIs but have issues with adherence and may break.
Are any forms of birth control 100% reliable?
No form of birth control is entirely reliable. However, methods like the IUD or IUS offer greater than 99% effectiveness. The contraceptive pill offers greater than 99% reliability too, if used correctly and regularly. Other methods are less reliable - the male condom for example is 98% effective, and natural birth control (although theoretically 99% effective) will normally be far less reliable than other options.
The only truly 100% reliable option is abstinence - but this is not a realistic or true option for the vast majority of people.
How do hormonal methods of birth control work?
Hormonal methods of birth control usually work to stop the process of ovulation, although they may also act on the mucus in the cervix, making it tougher for sperm to enter the uterus and fertilise an egg.
Oestrogen will prevent ovulation - an example birth control method that includes oestrogen is the combined pill.
Progestin acts on the mucus in the cervix and is contained in the combined pill too. It is also the hormone contained in the IUS and the implant.
How do non-hormonal methods of birth control work and can you name two different types?
The mechanism of action of non-hormonal methods depends on the specific type of birth control. I will therefore name two types and explain how they work. Perhaps the most obvious is condoms - condoms are a non-hormonal method that work by simply creating a barrier through which sperm cannot pass. The IUD (the copper coil) is another non-hormonal method. It works through the action of the copper itself, which prevents fertilisation or embedding of the egg.
Can you name two of the hormones used in birth control products?
Two hormones commonly used in birth control products are oestrogen and progestin.