Blood clotting is a healthy and helpful way for our body to heal after injury. However, when a clot develops in a vein or artery and obstructs blood flow, it becomes thrombosis. This can be fatal. One in four deaths worldwide have thrombosis as their underlying cause.
Throughout their life, women will face many choices that can contribute to their risk of thrombosis. These include decisions made around contraception and family planning, pregnancy and childbirth, as well as managing menopause symptoms. During their reproductive years, women have a higher risk of thrombosis than men. In recent years, thrombosis was the leading cause of direct maternal deaths in Australia.
According to Thrombosis Australia, blood clots are responsible for an estimated 10 per cent of all deaths in the country, but up to 70 per cent of these are preventable. Recognising the symptoms and planning ahead during times when you are at an increased risk are essential to help lower your chances of developing thrombosis.
Thrombosis or a blood clot?
Blood clots are clumps that occur when blood hardens from a liquid to a solid to prevent excess bleeding during injury. Usually, the body will naturally dissolve a blood clot after the wound has healed and it is no longer needed.
“Blood clotting is a complex process that … is controlled by a variety of different proteins and other chemicals,” says Natalie Raffoul, senior manager of Healthcare Programs and Clinical Strategy at the Heart Foundation. “Some of them promote blood clotting, while others act to prevent it, or break down clots that have formed. These things work in a balance to clot when we need to but keep our blood moving freely when we don’t.”
Venous thromboembolism (VTE) is a blood clot that forms in a vein. It can include deep vein thrombosis (DVT) and pulmonary embolism (PE). Each year, 30,000 Australians develop VTE, including both DVT and PE. Complications of thrombosis can be life-threatening and can include a stroke or heart attack.
DVT, the more common form of thrombosis in Australia, occurs when a blood clot develops in the deep veins of the lower leg, thigh or pelvis. They can also sometimes occur in the arm. A PE occurs when a blood clot from DVT breaks off and travels to the lungs where it becomes lodged in the pulmonary artery, which can be life-threatening. Pulmonary embolism is the third-leading cause of cardiovascular death, according to a report in the Australian Journal of General Practice.
Know the signs
The first step to prevention is understanding the symptoms. According to the National Blood Clot Alliance, “study after study has shown that fewer than one in four people have any recognition of blood clots or their signs and symptoms.”
The symptoms of a blood clot in the arm or leg include:
- Redness or discolouration of the skin
- Skin that is warm to the touch
- Pain or tenderness
- Swelling or throbbing in one leg
- Swollen veins that are hard or sore when you touch them
The symptoms of a blood clot in the lung include:
- Difficulty breathing, especially if it comes on suddenly
- Chest pain that’s worse when you breathe in, particularly a sharp, shooting pain
- Coughing up blood
- Feeling dizzy and lightheaded
- Faster-than-normal or irregular heartbeat
If you experience any of these symptoms, seek immediate medical help. For some, the symptoms may only be mild, while in some cases, there may be no symptoms at all. According to Thrombosis Australia, for those affected by pulmonary embolism, sudden death is the first symptom in almost 25 per cent of cases. That’s why being aware of how to prevent it is essential.
Women and thrombosis
The general risk factors for thrombosis, for all genders, are obesity, smoking, hospitalisation, long haul flights, having diabetes, a history of blood clots, (either individually or in the family), bed rest or extended period of inactivity or age (40+).
If you’re a woman, however, there are several other lifestyle factors that could increase your chances of developing thrombosis. While men have a higher risk of thrombosis than women after the age of 45, women are at higher risk during their reproductive years.
According to Raffoul, these risk factors include “pregnancy and the use of oestrogen-based medicines as contraceptives or to relieve some of the symptoms of menopause. Since thrombosis is often preventable, women can lower their risk by understanding its causes and taking steps to prevent it.”
The lifestyle risk factors for women are:
- Family planning and contraception
- Pregnancy, birth and for six-weeks postpartum
- Menopause and hormone-replacement therapy
Fluctuating oestrogen levels in the body can increase a woman’s risk of blood clotting. If you’re taking medication that will alter your oestrogen levels, be aware that your chances of developing thrombosis will be increased during this time. “Oestrogen is prothrombotic, meaning it promotes blood clotting. It increases the levels of proteins that encourage clotting, while reducing those that prevent it,” says Raffoul.
“We don’t know exactly how it does this, but research has shown that it may be different depending on the dose and the way oestrogen is given, for example either in a tablet or skin patch. This means that oestrogen-based medicines can change the amounts of these clot-controlling factors in your blood and tip the balance towards clotting.”
The pill
One of the most common reasons for a woman consuming oestrogen is as a form of contraceptive. The combined oral contraceptive, or the pill, contains both a synthetic oestrogen and another hormone called progesterone.
A report in the Australian Prescriber journal stated that the pill is the most commonly used contraceptive method by Australian women and approximately 50–80 per cent use it at some stage during their reproductive years. Yet according to Thrombosis Australia, the pill can increase your risk of developing thrombosis by two to three times. This is compared to those not taking it.
“Because of all the different doses and methods of administration, it is difficult to pinpoint the exact risk of taking an oestrogen-based medicine,” says Raffoul. “But it is important to note that even though there is an increased risk, the overall blood-clotting risk of taking these medicines is still very low.”
However, there are other factors that, when combined with using the pill, can further increase your risk. One factor is being overweight.
A research review published in ESC Heart Failure found that women who present both obesity and use of combined oral contraceptives (COC) have a greater risk of between 12 and 24 times of developing venous thromboembolism (VTE) than non-obese non-COC users.
While the risk is relatively small when using the pill, your doctor will be able to assess your personal risk factor of clotting. In some instances, they may prescribe an oestrogen-free, progesterone-only pill. This is often referred to as the “mini pill”. It is associated with a lower risk of clots, but is linked to other disadvantages such as acne and irregular menstrual bleeding.
Pregnancy
If a woman decides to get pregnant, this is a time when she will also be at a higher risk of thrombosis. Compared to non-pregnant women, the risk of VTE is increased by four to five times. In the postpartum period, up to six weeks after giving birth, the risk is even higher. 20-fold, according to a review published in the American Heart Association Journals.
This is because during pregnancy, a woman’s blood clots more easily to lessen blood loss during labour and delivery. Pregnant women may also experience less blood flow to the legs later in pregnancy. This is because the blood vessels around the pelvis are pressed upon by the growing baby.
According to clinical haematologist Dr Opelo Sefhore, who also serves as the clinical trials fellow at the Perth Blood Institute, “Venous-thromboembolic events were the leading cause of direct maternal deaths in Australia in between 2006 and 2016. This is from the Australian Commission on Safety and Quality in Healthcare, and it was responsible for about 10 percent of maternal deaths.”
Other factors can further increase the risk of clotting during pregnancy. According to Dr Sefhore, those at a slightly increased risk are patients over the age of 35, those that have had two or more previous pregnancies or if they are carrying twin or triple pregnancies.
“As the uterus expands, it compresses on the blood vessels in the groin, and that reduces the blood flow back to the heart and increases stasis [a situation where blood is not able to flow properly through the tissues] and that, in itself, increases your risk of clots,” explains Dr Sefhore. “And, obviously, if you’re carrying multiple pregnancies, the level of hormonal changes is slightly different to if you’re carrying just one pregnancy.”
I’m pregnant, am I at a higher risk?
During pregnancy, thrombosis is something that can be managed or prevented and should not cause panic or worry. If you are pregnant or planning to get pregnant, flag the following points if they apply to you and ask your doctor to take this into consideration when assessing your risk for thrombosis:
- A family history of blood clotting, gestational diabetes or pre-eclampsia
- If you are planning on delivery by C-section
- Are over the age of 35
- Are overweight or have a BMI higher than 30
- Have diabetes, heart disease or lung disease
- Are a smoker
- Have had two or more previous pregnancies
- Are carrying multiple babies
- Have ever had a blood clot before or have a genetic blood clotting disorder
Assisted reproduction and IVF
Conceiving through IVF or assisted reproduction increases the chance of getting thrombosis. The number of mothers becoming pregnant this way isn’t small. According to data from The Australia and New Zealand Assisted Reproduction Database (AN