Thrombophilia in Pregnancy: What Are Its Risks?

For years, attempts have been made to clarify the need to detect and treat thrombophilia in pregnancy. However, to date, no consensus has been reached.
Thrombophilia in Pregnancy: What Are Its Risks?
Maryel Alvarado Nieto

Written and verified by the doctor Maryel Alvarado Nieto.

Last update: 18 October, 2023

Under certain conditions, there is a greater predisposition to suffer a thrombotic event, especially in the venous circulation. Because this risk increases with gestation, it has been proposed to investigate the influence of thrombophilia in pregnancy. The aim of these studies is to determine the risk factors involved in this condition.

First of all, it should be noted that the term thrombophilia encompasses disorders that, in some way, increase the capacity to produce clots in the blood. These conditions can be hereditary or acquired (such as antiphospholipid syndrome). Although they aren’t very frequent, they cause conditions that require careful management.

Thrombosis and embolism: what do they mean?

When a blood vessel is injured, a series of mechanisms are activated that attempt to repair the damage in order to prevent possible hemorrhage. All these phenomena constitute hemostasis. In short, the elements that circulate in the blood pile up, covering the vascular lesion.

This forms a clot, which is called a thrombus. The adherence of the thrombus to the vessel wall is compromised by the blood circulation itself, and there is a risk of detachment. When this occurs, the clot is called an embolus, with the capacity to circulate in the bloodstream.

Therefore, the terms thrombosis and embolism refer to the pathology in which a clot blocks a blood vessel. The difference between the two is that, in thrombosis, the occlusion occurs at the same site where the thrombus was formed. Whereas in embolism, the thrombus breaks off and travels through the circulation until it obstructs the vessel.

Thromboembolism and pregnancy

Pregnancy is considered a prothrombotic state. This is due to the hormonal modifications that occur during pregnancy.

For this reason, some authors consider it vitally important to establish the risk of thrombophilia in pregnancy in all women. The aim is to prevent any complications arising from such a predisposition.

However, there is no consensus on this matter and the perspective has changed in recent years. Firstly, this is because thrombophilias are, in themselves, too infrequent in the general population for their investigation in each pregnant woman to be protocol.

Secondly, the studies available to date have their limits. This prevents the results from being accepted as undeniable. Likewise, as knowledge advances, the understanding of things changes. In fact, it’s common to find contradictory conclusions in some investigations.

Blood tests.
Routine pregnancy tests don’t always give indications of thrombophilia in the pregnant woman.

Is there any relationship with thrombophilia in pregnancy?

Several pregnancy conditions have been associated with placental insufficiency. This means that the maternal-fetal blood flow is compromised in some way, producing a complication.

Among the conditions that are linked to circulatory alterations are the following:

  • Eclampsia
  • Preeclampsia
  • HELLP syndrome
  • Intrauterine growth restriction
  • Premature detachment of the placenta

For this reason, some authors consider it necessary to suspect the existence of thrombophilia in patients with a history of any of these complications. The justification for this is not based on a possible association between both conditions, but to reduce the uncertainty of a woman with previous bad experiences.

Is thrombophilia in pregnancy associated with pregnancy loss?

Between 10 and 15% of pregnancies end in miscarriage; many of which go unnoticed. Of these women, it is estimated that 5% may experience another failed pregnancy. Thus, most women with a single history of miscarriage have a high chance of carrying a pregnancy to term.

This reality has called into question the need to thoroughly investigate the probable cause of pregnancy termination, especially if it’s a first attempt. Although it’s a traumatic event for the woman, it is far from being synonymous with infertility or predicting a future problem.

Recurrent pregnancy loss and thrombophilia

However, the same is not true if the experience is repeated. Recurrent pregnancy loss is considered if there are at least two consecutive miscarriages. However, some authors prefer to set the limit at three.

Regardless of the definition, this is an extremely difficult situation for the couple, who usually seek professional help. The purpose of this is not only to find a solution, but also to obtain an explanation. In these cases, current evidence doesn’t provide a consensus.

Is there a pattern with thrombophilia and miscarriage?

The gestational age of previous losses is important to guide the investigation, which must be individualized. In early pregnancy, an alteration in the constitution of the trophoblast may be implicated. This structure will later help to form the placenta.

While in later stages, miscarriages may be associated with vascular complications that compromise blood flow. However, due to the low incidence in the population, the general consensus is not to systematically look for hereditary thrombophilia in pregnancy.

What are the risks?

Thrombotic events contribute to the occurrence of gestational complications and are the leading cause of maternal death in developed countries. More than half of the cases are associated with an underlying thrombophilia, but most patients with thrombophilia have uncomplicated pregnancies.

So why the disparity? The answer isn’t found in an isolated predisposition for a thrombotic event, since pregnancy in itself is a risk condition, but to the superposition of several of these factors, among them, thrombophilia.

Some of the associated factors that increase gestational risk in a woman with thrombophilia are the following:

  • Obesity
  • Being a smoker
  • Physical rest
  • Recent surgery
  • High maternal age (over 35 years)

For this reason, the evaluation of the pregnant patient should focus on the identification of risk factors. The justification for investigating the possible existence of a thrombophilia should have a solid basis and not just be to an unnecessary systematic practice.

Pregnancy check.
Routine pregnancy controls do allow the detection of risk factors for early action.

Treatment of thrombophilia in pregnancy

For years there has been controversy about whether or not to treat patients with thrombophilia during pregnancy. The difficulty of this lack of consensus lies in the fact that the studies available are scarce and have several methodological drawbacks that limit their results.

However, several reviews don’t attribute a real benefit to treatment with low molecular weight heparin (LMWH) or acetylsalicylic acid (aspirin) as a way of preventing a thrombotic event in a pregnant woman with thrombophilia. For the choice of this type of therapy, it is necessary to treat each patient on an individual basis.

Therefore, it’s essential to trust the obstetrician who controls the pregnancy. It will be this expert who will define, according to the risk factors, the best preventive approach to arrive safely at delivery.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

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This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.