Thrombophilia Panel

The thrombophilia panel analyzes various genetic and biochemical markers to evaluate hereditary or acquired clotting tendency. The test holds clinical importance in determining the risk of venous thrombosis and objectively reveals individuals’ thrombotic predisposition.

This analysis evaluates the functioning of the coagulation system by examining genes such as Factor V Leiden and MTHFR. This approach contributes to forming a personalized risk profile.

Thrombophilia screening is performed in individuals with a history of recurrent thrombosis or unexplained pregnancy losses. Early detection allows planning prophylactic anticoagulant strategies and reduces the risk of complications in pregnancy management.

Monitoring the thrombophilia panel ensures long-term follow-up of thrombosis risk. Regular evaluation of results strengthens clinical management by personalizing the treatment process, shaping lifestyle recommendations, and preventing possible thrombotic events.

What Is a Thrombophilia Panel?

A thrombophilia panel is a series of blood tests performed to identify genetic or acquired risk factors that increase the individual’s tendency to clot. This panel is particularly used in recurrent miscarriages, pregnancy complications, or unexplained vascular occlusions. It includes genetic tests such as Factor V Leiden, prothrombin mutation, and MTHFR mutation, and plays an important role in treatment planning.

What is the relationship between pregnancy and the clotting system?

Pregnancy naturally creates a physiological “pro-clotting” state in the body. This is an evolutionary adaptation developed by the body to protect against severe bleeding during childbirth. Throughout pregnancy, factors that promote clotting increase, proteins that naturally inhibit clotting (especially Protein S) decrease, and the system that dissolves clots slows down.

This protective mechanism makes pregnant and postpartum women 4–5 times more at risk of clotting compared to non-pregnant women. This physiological change is critically important. Consider this: Many individuals with an underlying hereditary thrombophilia (such as Factor V Leiden carrier state) may never show symptoms throughout their lives. However, when exposed to a strong “second trigger” such as pregnancy or IVF treatment, these two factors may combine and elevate the clotting risk to clinically dangerous levels. If thrombophilia is the “first hit,” pregnancy acts as the “second hit.”

Why is the timing of these tests so important?

The timing of these tests is crucial for obtaining accurate results. Performing them at the wrong time may lead to completely incorrect diagnoses and unnecessary treatments.

For example, genetic tests (such as Factor V Leiden or Prothrombin) evaluate your DNA, so results never change throughout life. These tests can be performed during pregnancy, while taking medication, or during a clotting event; the results are always reliable.

However, the situation changes completely with functional tests (Protein S, Protein C, Antithrombin) and APS tests. Protein S, one of the body’s natural anticoagulants, physiologically decreases during pregnancy. If this test is done during this period, we may get a “false-positive” result as if there is a deficiency that does not actually exist. Similarly, values are not reliable when using anticoagulants (heparin, warfarin, etc.) or during an acute clotting attack. Therefore, the ideal timing for these functional tests is outside pregnancy, when not using anticoagulants, and at least 3 months after an acute clotting event.

For Antiphospholipid Syndrome (APS) tests, the golden rule is “persistence.” A simple infection can cause these antibodies to temporarily test positive. To diagnose APS, a positive test must be repeated at least 12 weeks later and confirmed. A single positive result is not sufficient for diagnosis.

Why does IVF treatment increase clotting risk?

Although the role of thrombophilia in miscarriage or implantation failure is controversial, the clotting risk created by IVF treatment itself is clear and well-established. This issue primarily concerns the safety of the mother.

In IVF treatment, controlled ovarian stimulation (COS) protocols are used to obtain multiple eggs. This treatment creates a supraphysiological hormonal environment in the body. Elevated estrogen levels intensely activate the clotting system and increase the tendency to clot.

This treatment-related risk reaches a critical peak when Ovarian Hyperstimulation Syndrome (OHSS), the most severe complication of IVF treatment, occurs. OHSS is characterized by increased vascular permeability, fluid accumulation in the abdomen and lungs, and blood concentration (hemoconcentration). This condition can increase the risk of clots up to 100-fold in both veins and (rarely) arteries.

This clear and present danger changes the purpose of the thrombophilia panel in the IVF process. The aim is not to predict or improve pregnancy rates but to identify patients who will be at extremely high risk of clotting when the ovaries are stimulated or if OHSS develops, ensuring maternal safety. An OHSS case in a patient with underlying thrombophilia represents one of the most dangerous “two-hit” scenarios.

Does clotting tendency cause recurrent miscarriages?

The answer depends on the type of thrombophilia — a very important distinction. Scientific evidence clearly separates two conditions:

• Acquired Thrombophilia (Antiphospholipid Syndrome – APS)
• Hereditary Thrombophilia (Factor V Leiden, Prothrombin, etc.)

The relationship between APS and recurrent pregnancy loss is strong and well-proven. It is even one of the diagnostic criteria. These antibodies are thought to cause pregnancy loss by forming small clots (microthrombosis) in the placental vessels and by creating a direct inflammatory effect on the trophoblast cells responsible for placental implantation.

However, when it comes to hereditary thrombophilias (Factor V Leiden, Prothrombin mutation, etc.), the evidence is much weaker and controversial. Some studies show a small statistical association between these mutations and recurrent miscarriages, but the absolute risk is very low.

More importantly, the key information in this group is this: In women with hereditary thrombophilia (without APS) and recurrent miscarriages, there is no strong scientific evidence that anticoagulant treatment (aspirin or injectable blood thinners) prevents miscarriage or increases live birth rates. Therefore, major medical guidelines do not recommend hereditary thrombophilia screening or treatment based solely on this indication.

Does clotting tendency prevent embryo implantation?

Recurrent implantation failure (RIF), meaning failure to achieve pregnancy despite transferring good-quality embryos, is one of the most challenging aspects of IVF treatment. Whether thrombophilia can contribute to this has been investigated for many years.

However, evidence linking thrombophilia to RIF is much weaker and more inconsistent compared to recurrent miscarriage. A major contradiction is seen in studies: Some retrospective, lower-quality studies suggested an association, but prospective cohort studies, which provide stronger scientific evidence, did not show a meaningful link between hereditary or acquired thrombophilia and embryo implantation or live-birth rates.

Because stronger studies do not confirm this association, major guidelines such as the American Society for Reproductive Medicine (ASRM) do not recommend routine thrombophilia screening solely for RIF.

Should everyone undergoing IVF have a thrombophilia panel?

In light of evidence-based medicine, the answer is clearly No.

Routine thrombophilia panel screening is not recommended for every couple starting IVF treatment or for every infertility patient. This approach represents a “one-size-fits-all” mentality, which has no place in modern medicine. Instead of testing everyone, a selective screening strategy should be applied, focusing on those who truly need the test.

So who should consider thrombophilia testing?

The decision to test is based on whether the result will meaningfully change clinical management and treatment planning. Taking a comprehensive medical history is crucial. Testing is primarily recommended in the following situations where results may influence treatment:

For APS (Antiphospholipid Syndrome) Panel:

• Three or more consecutive pregnancy losses before the 10th week
• One or more unexplained fetal deaths at or after the 10th week
• Severe preeclampsia or placental insufficiency resulting in preterm delivery before 34 weeks

For Full Thrombophilia Panel (Hereditary + Acquired):

• A personal history of clotting (VTE), especially if unprovoked
• A personal history of clotting triggered by estrogen (birth-control pills or pregnancy)
• A first-degree relative (mother, father, sibling) with a known high-risk hereditary thrombophilia (e.g., Antithrombin deficiency, homozygous FVL)

What treatments are applied if thrombophilia is detected?

The main anticoagulant (blood-thinning) agents used during IVF and pregnancy are two:

• Low-molecular-weight heparin (LMWH – “blood-thinner injection”)
• Low-dose aspirin (LDA)

LMWH is the preferred anticoagulant in pregnancy. Its most important feature is that it does not cross the placental barrier, therefore does not reach the baby. Its effect is more predictable, and it is much safer and easier to use than older forms of heparin. Aspirin mainly works by preventing the aggregation of platelets, which are clotting cells.

What is the main goal of treatment? Improving implantation or protecting the mother?

This is perhaps the most critical distinction in the entire topic. When starting anticoagulant therapy, we must clearly distinguish why these medications are being used. Treatment has two separate and distinctly different purposes:

PURPOSE 1: Improving Pregnancy Outcomes (Increasing Live-Birth Rates)

There is only one scenario in which treatment has been proven effective for this purpose:

• Confirmed Obstetric Antiphospholipid Syndrome (APS)

These patients have a history of recurrent pregnancy loss and confirmed APS positivity with tests repeated 12 weeks apart. In this specific group, low-dose aspirin and LMWH have been clearly proven in strong scientific studies to increase live-birth rates.

PURPOSE 2: Protecting the Mother (Preventing Clotting)

Here, the aim is not to increase fertility but to protect the mother’s health and life in high-risk situations. This treatment is applied in the following cases:

• Those with a personal history of clotting (VTE) — pregnancy and IVF significantly increase the risk of a new clot
• Those with known high-risk hereditary thrombophilia (e.g., homozygous FVL, Antithrombin deficiency)
• Patients who develop Ovarian Hyperstimulation Syndrome (OHSS)

This distinction is extremely important. In women with unexplained miscarriages or only low-risk hereditary thrombophilia (such as heterozygous Factor V Leiden), anticoagulant therapy is not recommended for the purpose of “helping pregnancy,” because studies show that it does not increase live-birth rates. Treatment should be reserved only for those who will truly benefit.

What is done for clotting risk if OHSS develops?

Moderate to severe OHSS is a serious condition that can increase clotting risk up to 100-fold. It is an IVF treatment complication and becomes a primary safety concern for the mother.

As soon as OHSS is diagnosed, prophylactic LMWH is strongly recommended for maternal safety, even if the patient has no underlying thrombophilia. If pregnancy is achieved in that treatment cycle, therapy continues through the first trimester, the period when clotting risk is highest. The sole aim here is to protect the mother from a dangerous clotting event during this severe treatment-related complication.

Frequently Asked Questions