Clotting tests are not necessary for everyone having IVF, but a personal or family history of blood clots or repeated pregnancy losses may make them worth discussing with Kristýna Frühaufová, PhD, Head Physician at GYNEM Fertility Clinic.
Thrombophilia means that blood clots more easily than usual. In IVF and pregnancy, concern centres partly on the possibility that small clots could form around the time an embryo implants or as the placenta develops. These clots may interfere with placental development and, in turn, embryo development.
Thrombophilia may contribute to miscarriage or restricted fetal growth, but it is only one possible explanation for pregnancy loss—and one of the less common ones. A miscarriage does not, by itself, mean a clotting disorder is probably responsible. Age and other factors matter when deciding what to investigate.
The same caution applies to repeated implantation failure, when embryos repeatedly do not implant. Whether thrombophilia is responsible can be difficult to determine, and an underlying immunological issue may also be considered. A clotting test is therefore one possible part of an investigation, rather than a way to explain every unsuccessful transfer.
The clearest reason to discuss testing is a personal history of a blood clot, particularly one that occurred at a young age. A previous pulmonary embolism, or clot in the lung, is also relevant. Clots associated with hormonal contraception or an injury are among the experiences to bring to a clinician’s attention.
Family history can help guide the decision, too. Clotting at a younger age in a parent or sibling is a reason to consider testing. If a close relative has already tested positive for an inherited clotting disorder, other family members may be advised to have genetic testing.
Pregnancy history is another part of the conversation. Testing may be considered after two or three miscarriages, particularly at a younger age. In IVF, it may also be considered after two or three pregnancy losses involving good-quality embryos or euploid embryos, which have been tested for chromosome number.
These histories do not all call for the same tests. A clinician investigating a known mutation in a family may choose a different approach from one investigating repeated miscarriages. That distinction matters when deciding whether a test panel is useful for an individual patient.
Some clotting tendencies are inherited through gene variants. Two of the most commonly tested are factor V Leiden and the factor II prothrombin mutation. An inherited thrombophilia lasts for life, so its test result remains relevant beyond a single IVF cycle or pregnancy.
Other clotting conditions are acquired later in life. The most common acquired example in the notes is antiphospholipid syndrome, an immunological condition associated with antibodies. Unlike an inherited mutation, acquired thrombophilia may appear and disappear over time.
That difference can affect how a clinician interprets test results. Antibodies associated with acquired thrombophilia may be present only during certain periods of life, and they may be associated with autoimmune conditions or appear after a viral infection. A patient’s results need to be considered alongside their medical and pregnancy history.
There is no single panel that answers every question. If a family member has an identified mutation, testing can focus on that mutation. If the family mutation is unknown, a basic inherited-thrombophilia panel may include factor V and factor II testing.
When repeated miscarriage is the concern, the investigation may also look for antiphospholipid antibodies. The main blood tests are lupus anticoagulant, anticardiolipin antibodies and anti-beta-2 glycoprotein I. These tests address a different question from inherited mutation testing: whether an acquired antibody-related condition may be involved.
A more expensive panel is not automatically the right choice for every patient. Its value depends on what the clinician is trying to find. For someone with repeated miscarriages, for example, lupus anticoagulant testing may be worth including if it was not part of an earlier panel.
Before paying for additional testing, patients can ask which result would change their care. It is also useful to share any previous results and details of a relative’s diagnosed mutation, if known. The aim is to select tests that fit the reason for the investigation, rather than simply choosing the longest list.
MTHFR is not generally treated as a thrombophilia disorder in this context and is not part of a thrombophilia workup. A positive MTHFR result does not, on its own, mean that a patient needs blood thinners. Another indication, such as a separate thrombophilia or a history of repeated miscarriages, would need to be considered.
Heparin and other blood thinners may be used when there is a medical reason to reduce clotting risk. Giving heparin to all IVF patients without testing does not improve IVF success rates. Treatment decisions instead depend on the patient’s diagnosis and history.
For a patient with a Leiden or prothrombin mutation but no history of deep venous thrombosis, injections are not necessarily needed while preparing for embryo transfer. If pregnancy occurs, blood thinners are usually added and continued throughout pregnancy and for six weeks postpartum. The plan may differ when a patient has a different history or diagnosis.
Antiphospholipid syndrome is one of the situations in which a blood thinner and low-dose aspirin may be used together. The timing of treatment should be discussed with the clinician managing the patient’s care, particularly when antibody results have differed over time. A past positive result and a later negative result are not a reason to set a medication schedule without that discussion.
For patients with repeated pregnancy losses but no identified thrombophilia, the decision can be less clear. There is limited medical evidence that adding blood thinners after a positive pregnancy test changes outcomes. Other potential causes, including anatomical and immunological issues, may need to be considered before treatment is discussed.
Frühaufová would consider blood thinners for some patients with repeated losses when other possible causes have been ruled out, and blood thinners are the remaining intervention. In a patient with negative thrombophilia and antiphospholipid testing, her approach would be to start after embryo transfer rather than before it. That is an individualised approach, not a recommendation that everyone with an unsuccessful transfer should take blood thinners.
Blood-thinner injections can cause bruising and bleeding. They also require daily injections, which some patients may find difficult to give themselves. Those practical demands belong in the decision alongside the potential benefit.
Patients can ask why treatment is being proposed, when it would start and how long it would continue. They can also ask what a test result would mean for an embryo transfer plan or a future pregnancy. A clear medical reason and a shared decision between patient and physician are especially important when treatment involves daily medication.
A clotting disorder is worth investigating for some IVF patients, particularly those with a personal or close family history of clots or repeated pregnancy losses. For others, routine testing or blood-thinner injections may add burden without improving the chance of success. The most useful next step is a conversation grounded in the patient’s own history, so that testing and treatment have a clear purpose.
No. Thrombophilia testing is not needed for everyone undergoing IVF.
It depends on the reason for testing. A more expensive panel may include tests not covered by a cheaper one, such as a coagulation profile, antithrombin III, fibrinogen, lupus anticoagulant, protein C, free protein S antigen and anticardiolipin antibodies.
For someone with a history of repeated miscarriages, lupus anticoagulant testing is worth doing, and the more extensive panel is preferable in that setting. The clinician and patient should decide on the indication together. The choice depends on whether the aim is to identify an inherited disorder based on medical or family history, or to investigate the cause of recurrent miscarriages.
This is a difficult question. There is limited medical evidence that adding blood thinners after a positive pregnancy test changes outcomes. However, if a patient has recurrent pregnancy loss and blood thinners are the only remaining intervention, adding them is an option.
If the miscarriages are not very early—for example, not in the fifth week—blood thinners may be considered as part of a clinical trial approach.
For a patient who has experienced recurrent implantation failure and pregnancy losses, including a miscarriage after transfer of a good-quality euploid embryo, blood thinners may be added if thrombophilia and antiphospholipid syndrome tests are negative, other possible causes such as anatomic and immunological issues have been ruled out, and blood thinners are the only option left.
In this situation, they would be started after embryo transfer, not before. Without evidence of an inherited coagulation disorder, there is no indication to begin earlier. The aim is to prevent clotting at the placental site, and the placenta forms later in pregnancy.
For antiphospholipid syndrome, a combination of baby aspirin and a blood thinner is recommended. Although these medications are usually used separately, antiphospholipid syndrome is one of the few indications where both are used at the same time.
For a patient with one positive lupus anticoagulant test and a negative test seven months later who is planning a modified natural embryo transfer, aspirin would be started at the beginning of the cycle and the blood thinner added after embryo transfer.
Increased activity suggests that something is likely going on. The explanation may be the Leiden mutation itself, because increased activity is the phenotype of the underlying gene mutation.
The first step is to test for the Leiden mutation. It is likely to be confirmed and may explain the early miscarriage. Blood thinners might help.
Not necessarily. A positive MTHFR result alone does not indicate a need for blood thinners. There would need to be another indication, such as another thrombophilia or a history of repeated miscarriages.
