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 (ANZARD), 20,000 babies are born from IVF treatment in Australia each year, representing one in 18 children. This rises to one in 10 children born to mothers aged 35 years and older.

“Patients who have IVF or reproductive assisted services have a higher risk than if you have a natural conception,” says Dr Sefhore. “That’s because they have artificially high levels of oestrogen, or hormones, at the time that they are trying IVF, so they are at an increased risk of thrombosis.”

A study published in the British Medical Journal (BMJ) compared the risk of PE and VTE in women undergoing IVF pregnancy and women undergoing natural conception. It found the risk of VTE for IVF-pregnant women was 4.2 in 1000, but just 2.5 in 1000 for women who fell pregnant naturally. The risk of VTE was increased during the whole pregnancy, but particularly during the first trimester. The risk of pulmonary embolism in women who fell pregnant through IVF was three in 10,000, compared to 0.4 in 10,000 for spontaneous pregnancies.

The delivery room and beyond

Regardless of whether you become pregnant through IVF or by natural conception, a conversation with your doctor is key to early diagnosis of thrombosis and prevention — together, you can form a management plan. This is especially important if you have had thrombosis before or are considered in the high-risk category.

“For women who have a previous history of thrombosis, we always recommend that they get seen by a haematologist as soon as they find out that they’re pregnant, because they will need ongoing haematology management throughout their pregnancy,” says Dr Sefhore.

Management is often done using prophylactic blood thinners, meaning a slightly lower dose of medication than if treating an active clot. “Unfortunately, the only downside is that it’s only in the form of an injection,” says Dr Sefhore. “That’s the safest treatment that we can give, because it has no effect on the baby.”

A management plan not only lowers the risk of blood clots but can also help reduce your anxiety and uncertainty. “It has to be very tightly managed by a multidisciplinary team, so haematologists, obstetricians and paediatrics are all involved,” explains Dr Sefhore. “But it’s very safe if we do it in that manner. Delivery can be in the form of whatever the patient chooses, so natural vaginal delivery or if they want a caesarean, we can always support them, as long as we have a plan in place.”

The chances of developing thrombosis don’t disappear after delivery of the baby. During the six-week postpartum period, women are also at a heightened risk. This is due to hormonal changes during pregnancy that create a hypercoagulable state, meaning the blood is more prone to clotting. This is combined with potential complications such as prolonged immobility after delivery or recovery from a C-section.

Hospitalisation and surgery

Alongside having a C-section, other major surgeries on the abdomen or lower body are also a risk factor, such as having a hysterectomy, a surgical procedure to remove the uterus. This is usually due to being inactive while on bedrest.

Being immobile for prolonged periods of time increases your chances of developing thrombosis because it can cause blood to pool in your legs. According to the Australian Commission on Safety and Quality in Healthcare, many of the 30,000 Australians that develop blood clots each year develop them during or following a hospital stay, and an estimated 5000 people die each year as a result of hospital-acquired VTE.

“Hospital stays are a significant risk factor for VTE, accounting for nearly 10 per cent of in-hospital deaths,” says Raffoul. “In fact, VTE is one of Australia’s leading causes of preventable death. More specifically, nearly 95 per cent of people who develop VTE in hospital have just had surgery. Orthopaedic surgeries (such as hip and knee replacements) are the most likely to lead to blood clots.”

Being active while you rest and recover

A hospital stay can be an opportunity to rest and binge-watch your favourite show. However, it’s important to incorporate activity and movement as soon as you’re able to. How often you do this, and what type of movement you can do, will depend on your surgery type and recovery plan. Your doctors will advise you and this may be assisted with the use of blood-thinning medication or compression stockings.

“Getting out of bed with the help of a physio or nurse and walking is the best way to be active,” says Raffoul. “They will let you know when you can do it alone. But if you can’t do that, research has shown that even movements of your feet and ankles can be enough to get your blood moving and reduce your risk of developing thrombosis.”

Menopause management

According to the Australasian Menopause Society, there are more than two million postmenopausal women in Australia. A study found that around 13 per cent of menopausal women in their 50s and 60s use HRT to manage their symptoms such as hot flushes and night sweats.

A study published in the BMJ found that the risk of developing thrombosis was increased for women using HRT in tablet form. The risk was slightly increased the higher the dose. Women taking HRT tablets were up to two times more likely to be at risk compared to other forms (such as patches, gels or creams).

Taking HRT through other forms was not found to increase the risk. This is because the oestrogen in tablets is processed through the liver, which can trigger the production of clotting factors, while transdermal forms deliver oestrogen directly through the skin, bypassing the liver and therefore not causing this clotting effect.

Regardless of whether HRT is used, women who experience early menopause, before the age of 40, or late menopause, after 55, have a higher chance of developing thrombosis and heart disease. This is because during early menopause, the body experiences a quicker decline in oestrogen, while in late menopause, the body experiences prolonged exposure to oestrogen. These fluctuations in oestrogen levels can influence the blood’s clotting mechanisms.

Prevention

There are general lifestyle changes you can make to lower your risk of developing thrombosis. These include:

• Staying active. Even just moderate exercise can help lower the risk of clotting, such as swimming, yoga and walking. “Aim for at least 150 minutes of moderate exercise weekly,” advises Raffoul.
• Eating healthy. Minimise sugar and trans fats and limit red meat consumption. “Focus on a balanced diet rich in fruits, vegetables, wholegrains and lean proteins,” says Raffoul
• Maintaining a healthy weight. Women with a BMI over 30 have a higher chance of developing thrombosis.
• Doing your research. Where possible, find out your family history of blood clotting and other risk factors.
• Staying hydrated. Aim to drink about eight cups of water each day.
• Quitting smoking. Smokers are at a higher risk of developing clots. Chemicals in tobacco smoke make certain proteins in your blood “stickier”.
• Travelling smart. If you are taking a long-haul flight, or another journey over four hours, be sure to stand up and move around every couple of hours if you’re able to. If not, roll your ankles and flex your calf muscles. Drink plenty of water to stay hydrated. The Aerospace Medical Association suggests drinking about 230mL for every hour you’re in the air.
• Moving while ill. If you’re unwell with the flu, COVID-19, premenstrual syndrome (PMS), period pains or another illness that would require you to be in bed for several days, be sure to get up and move around every few hours, even if it’s only to use the bathroom, get a glass of water or do a couple of slow laps around your home

Know the symptoms

Implementing these preventative measures is essential. If you’re a woman, this is particularly important around the moments or milestones when you are more at risk. These include,  pregnancy, postpartum and when taking oestrogen-based medicines.

If you have had a blood clot previously, it’s even more important to stay vigilant about the symptoms of a recurrence. According to the US Centers for Disease Control and Prevention (CDC), one third (33 per cent) of people who experience a VTE event will experience a recurrence within the following 10 years.

Remember that everyone is at risk. Even if you aren’t in the high-risk category or think none of the risk factors apply to you. According to the National Blood Clot Alliance, around 30 per cent of blood clots are unprovoked. Meaning, there is no identifiable risk factor.

Understanding the symptoms and recognising them, either in yourself or someone close to you, could save a life

Article featured in WellBeing 217