The body goes through many changes during pregnancy however it is important to understand the difference between normal physiological differences that occur and ones that are caused by disorders or other factors. These may have an impact on the pregnancy and birth.

Thrombosis

During pregnancy the coagulation system alters to a hypercoagulable situation to prepare for haemostasis during delivery. Haemostasis is the process involved in the cessation of bleeding. This increase in certain clotting factors elevates the risk of thrombus formation.

Pregnant women are 5-10 times more likely to experience a blood clot compared with non-pregnant women of similar age. Women who are already on anticoagulants and are planning to become pregnant, the type of oral anticoagulant (OAC) is important. PBI webpage - pregnancy and thrombosis.

Factor V Leiden

Factor V Leiden is a genetic mutation which increases the possibility of blood clots. Pregnant women with this mutation have a 2 to 3-fold increased risk for pregnancy loss and perhaps other obstetric complications. PBI webpage - Factor V leiden.

von Willebrand disease (VWD)

This is an inherited bleeding disorder where the blood does not clot property. VWD involves low levels or underperforming von Willebrand factor (VWF) which is a vital protein required for the blood clotting process.

VWF works in conjunction with another clotting protein Factor VIII and both increase during pregnancy. These two proteins facilitate haemostasis after childbirth, which is the body’s response to stop bleeding. Excess gynaecological bleeding is increased in women with VWD, with post-partum haemorrhage increasing 1.5 times; with a 5-fold risk of blood transfusion, and a higher risk of death by 10-fold. There is also an increased risk of post-partum bleeding up to 6-weeks following delivery, 30% compared to 2% among women who do not have VWD.

Platelet disorders

Thrombocythaemia is a blood disorder where the body produces elevated numbers of platelets which can lead to blood clots. Pregnant women with thrombocythaemia have an increased risk of complications during pregnancy. PBI webpage - thrombocythaemia

Thrombocytopenia is a blood-related condition where the platelet count in the blood is very low. The condition is the second most common haematologic abnormality confronted during pregnancy. Gestational thrombocytopenia accounts for approximately 70-80% of cases and generally presents in the 2nd or 3rd trimester. The condition usually does not produce any symptoms and platelet levels commonly return to normal post-partum; however, complications can occur in 7% to 10% of pregnancies.

Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder involving blood clots (thrombi), platelet deficiency (thrombocytopenia) and bleeding problems presenting as bruising under the skin (purpura). Pregnancy is an influencing factor for the development of acute episodes of TTP and occurs in 1 in 25,000 pregnancy, mainly in the 3rd trimester or during puerperium. PBI webpage - TTP.

Other blood disorders

Anaemia during pregnancy is commonly due to iron or folate deficiency, however an increase in plasma volume and haemoglobin levels causes plasma levels to rise disproportionately around the sixth week point leading to haemoglobin levels to decline resulting in anaemia. A research review from 2022 found there was a high prevalence of anaemia among pregnant women, with the third trimester showing the highest rates. PBI webpage - anaemia.

Thalassaemia is a blood disorder that involves a reduced production of haemoglobin genes. Women with this disorder may have a reduced ability to become pregnant, with an elevated possibility of health risks during pregnancy. PBI webpage - thalassaemia.

Sickle cell disease (SCD)

This condition is an inherited life-long blood disorder where the haemoglobin in red blood cells (RBCs) is abnormal and causes the RBCs to become hard and sticky. This abnormality makes the RBCs inflexible and look C-shaped or like a sickle, rather than round, flexible and healthy.

As pregnancy is thought to be a prothrombotic state, and SCD can involve elevated coagulation events, pregnant women with SCD are shown to be at a higher risk of thromboembolism.

A 2023 study found that thromboembolism during pregnancy and 1-year post-partum was significantly higher in pregnant women with SCD when compared to pregnant women without SCD. The study results also found that thromboembolism was more prevalent during the third trimester and 3-months post-partum.

If there is a family history of any blood disorders or previous thromboembolic events, talking to your GP when planning pregnancy may be beneficial. Also, if you experience any unusual pain or bleeding, speak to your healthcare provider.

• National Institute of Health - Thrombocytopenia
• National Institute of Health - Thrombocytopenia in Pregnancy
• Gernsheimer, T., James, A. H., & Stasi, R. (2013). How I treat thrombocytopenia in pregnancy. Blood, 121(1), 38–47. https://doi.org/10.1182/blood-2012-08-448944
• Soma-Pillay, P., Nelson-Piercy, C., Tolppanen, H., & Mebazaa, A. (2016). Physiological changes in pregnancy. Cardiovascular Journal of Africa, 27(2), 89–94. https://doi.org/10.5830/CVJA-2016-021
• Sikka, P., Chopra, S., Aggarwal, N., Suri, V., & Chandrasekaran, A. (2013). Thrombotic thrombocytopenic purpura in the first trimester of pregnancy. Asian Journal of Transfusion Science, 7(1), 79–80. https://doi.org/10.4103/0973-6247.106746