The Risk Of Blood Clotting With Birth Control Pills

Chances are, you might have heard about birth control pills (BCP) because they are a fairly common type of medication these days. They are an excellent way of preventing unwanted pregnancies, family planning, and they can also be used to treat certain menstrual disorders such as heavy or extremely painful periods. 

BCP contain the female sex hormones oestrogen and progesterone, which essentially “tricks” the body into thinking it is already pregnant, preventing the release of the egg from the ovaries. When no eggs are released from the ovaries, conception cannot happen. 

Despite its success, there are some concerning side effects  but these are very rare and many people can use BCP successfully without ever experiencing them. One of these side effects is an increased risk of blood clots, which can be quite dangerous and at times, even fatal.

Understanding blood clots 

Whenever a part of the body is hurt, the body activates a mechanism to help heal the injury, known as blood clotting.¹ It helps seal any breakage in the skin and prevent further blood loss by forming a sort of “plug” formed from platelets. Whilst this is an important phenomenon for the body's self-protection, too much blood clotting can also be harmful. When a blood clot forms in the blood abnormally due to certain medications or medical conditions, it can circulate in your bloodstream and get stuck somewhere in the body, causing obstructions  known as a thromboembolism (TE). TEs can be dangerous as they can lead to heart attacks, strokes and pulmonary embolisms. 

There are three main types of TEs; venous, coronary and pulmonary. A venous TE can occur in any artery or vein in the body but most commonly occurs in the legs. A coronary TE occurs in the heart and obstructs blood flow to the heart, causing a heart attack. If a clot travels to the lungs and causes an obstruction in an artery in the lung, it is called a pulmonary embolism. 

The certain factors which can increase the risks of the formation of blood clots in our bodies are:² 

• Obesity
• Increasing age
• Smoking 
• Increased levels of oestrogen in the body - which can occur if you are pregnant, taking birth control pills or having hormone replacement therapy
• Long periods of inactivity such as long plane/car rides or being on bed rest for a prolonged period
• Blood clotting disorders which can either be acquired after birth or inherited from your parents
• Certain cancers
• Medical conditions such as high blood pressure, high cholesterol, diabetes, or conditions of long-term inflammation
• Trauma or surgery 

Mechanism of birth control pills

Hormonal contraceptives such as BCP are quite a popular method of contraception. They are made of synthetic female sex hormones and they can either be a combination of oestrogen and progestin or progestin on its own. 

BCPs prevent the release of an egg from the ovary each cycle (ovulation), preventing fertilisation as there is no egg available for sperm to fertilise. However, this is not the only way in which BCPs prevent pregnancies. They also thicken the mucus  found at the entrance of your cervix,  to make it more difficult for sperm to enter and reach the egg. They also make the lining of your uterus thinner to hinder the attachment of the fertilised egg to the lining of the uterus (a process known as implantation).³ 

There are various types of hormonal contraceptives besides BCPs, such as: 

• Intrauterine device (IUD)
• Injections
• Vaginal rings
• Skin patches 

BCPs must be taken daily at roughly the same time each day for about 21 days. Then for 7 days you will either stop taking the pills or take a placebo pill which contains no hormones. During these 7 days, you will likely menstruate as you are not ingesting any hormones. It is important to be very compliant with BCPs, as even missing one day can reduce the effectiveness of these pills and even result in a pregnancy. You might have to find additional alternate forms of contraception if you experience any vomiting or diarrhoea whilst taking BCPs as they might not get absorbed. It is also important to note that the effectiveness of BCPs can be hindered by the concurrent use of antibiotics, medications that lower blood pressure or cholesterol levels, or antifungal drugs. 

As with any chosen contraceptive method, there are some advantages and some disadvantages. Some advantages associated with BCPs are: 

• You do not have to interrupt or plan sexual intercourse around contraception
• It may result in lighter and less painful periods
• There is some evidence that BCPs can protect against ovarian, uterine and colon cancer⁴

Some disadvantages are mild side effects you can experience such as: 

• Breast tenderness
• Nausea
• Light bleeding 
• Mood changes 

There are some more serious side effects to watch out for such as: 

• Increased risk of blood clots
• Slightly increased risk for developing cervical and breast cancer⁴
• Severe stomach pain

Types of blood clots associated with birth control pills

Venous thromboembolism (VTE): these are blood clots which can form in the veins and usually occur after a major injury, major surgery, or during infections, inflammation, or long periods of rest. 

There are two main types of VTE; deep vein thrombosis (DVT) and pulmonary embolism (PE)

• DVT: these clots usually occur in the pelvis, thigh, or lower leg area but can also occur in the arms. You might notice signs and symptoms such as throbbing, warmth, redness and swelling in one leg, and swollen, sore veins. It is important to seek urgent medical help if you are experiencing any of these symptoms whilst taking BCPs. 
• PE: at times, a part of the clot which occurs during DVT can break off and travel to the lungs and cause an obstruction in a lung artery, inhibiting blood flow to a lung artery. This can lead to a dangerous and life-threatening condition known as PE. You might experience the sudden appearance of symptoms such as chest pain, difficulty breathing, and coughing up blood. You will need urgent medical attention if you start to experience these symptoms. 

Stroke and Heart attack: Sometimes, a blood clot might break off and travel to the heart, causing a blockage of blood to a heart artery, causing a heart attack. If the blood clot travels to the brain, it can lead to a stroke. 

Minimising risks and preventive measures 

Due to the risk of blood clots with the use of BCPs, it is important to undergo a basic screening before you start taking this form of contraception.⁵ Your doctor might ask you about any history of blood disorders or blood clots that run in your family or if you previously experienced any episodes of blood clotting. They may order some basic blood tests, including tests to check your liver and kidney function. You will also need to inform your doctor of any other medications you are taking, as some can hinder the effectiveness of BCPs such as blood pressure lowering and cholesterol-lowering medication. 

It might also be beneficial to bring about some lifestyle changes whilst taking BCPs, to further minimise the risk of clots. You should exercise regularly and avoid prolonged periods of being inactive, especially during long journeys such as plane journeys. You should avoid smoking and try to eat healthy and nutritious meals. It is important to keep a close eye on any new or worrying side effects and to check in regularly with your doctor. 

If you have a history of blood clots or a family history of blood clots/blood disorders, your doctor might decide that BCPs are not for you because taking them can greatly increase your risk of developing blood clots. However, there are numerous other forms of contraception which can be used, some of which are hormonal forms of contraception such as IUDs, or some that act as a barrier such as condoms. 

Summary

BCPs are a popular choice of contraception because they’re easy to take and very effective, being used to prevent unwanted pregnancies, treat heavy and painful periods, and regulate irregular menstrual cycles.  BCPs work by preventing ovulation, increasing the thickness of the mucus at the cervix and preventing any implantation of fertilised eggs. 

As with any medication, you can expect some side effects with BCPs, some more dangerous than others  such as the formation of blood clots. BCPs can increase the risk of blood clots which can lodge themselves somewhere in the bloodstream and cause an obstruction. This can lead to dangerous conditions such as PE, DVT, strokes and heart attacks.

Therefore, it is important to be assessed by a doctor before starting BCPs, and they should be avoided if you are taking certain medications or if you have a history or family history of blood clotting disorders or blood clots. There are numerous other forms of hormonal and non-hormonal contraception which can be explored further if you discover that BCPs are not the best choice for you.