Recurrent Pregnancy Loss: Causes Tests | Nawat Lab - Nawat Lab

Experiencing a pregnancy loss can be emotionally and physically challenging. These feelings of anxiety and uncertainty may become even more difficult when pregnancy loss occurs more than once. It is natural for couples to look for an explanation and want to know whether an underlying health condition can be identified or managed before trying to conceive again.

There are several possible causes of recurrent pregnancy loss, including chromosomal abnormalities in the embryo, certain immune and blood-clotting disorders, uterine abnormalities, and hormonal conditions. In some cases, however, no clear cause is identified despite an appropriate medical evaluation. Therefore, diagnosis does not depend on a single test but requires a structured assessment to determine which investigations are most useful for each individual.

Medical organizations differ in some aspects of when to begin the evaluation and which specific tests to recommend. However, they generally agree on the importance of avoiding unnecessary investigations and not using medications or blood thinners without a confirmed medical indication.

In this article, we explain the definition of recurrent pregnancy loss, the main tests recommended by medical guidelines, and the investigations that are not routinely advised for every case.

What Are the Causes of Recurrent Pregnancy Loss?

Several factors may explain repeated pregnancy loss. Having more than one miscarriage does not necessarily mean that the same cause is responsible each time, or that the problem lies with the woman alone. Some causes may involve the embryo or factors affecting both partners.

The most common potential causes of recurrent pregnancy loss include:

Chromosomal abnormalities: Changes in the number or structure of the embryo's chromosomes are an important cause of pregnancy loss. These abnormalities may occur randomly during egg or sperm formation or after fertilization. The likelihood of some chromosomal abnormalities increases with maternal age.
Antiphospholipid syndrome (APS): This is an acquired autoimmune disorder in which certain antibodies are associated with an increased risk of blood clots and pregnancy complications. It may contribute to recurrent pregnancy loss.
Uterine abnormalities: These include a uterine septum, certain fibroids that affect the uterine cavity, and intrauterine adhesions. Such abnormalities may interfere with embryo implantation or the continuation of pregnancy.
Thyroid disorders: Untreated hypothyroidism may be associated with an increased risk of pregnancy loss. A doctor may therefore request TSH and other thyroid function tests depending on the individual's condition.
Certain hormonal and metabolic disorders: These may include poorly controlled diabetes or elevated prolactin levels in specific cases.
Age-related factors: The risk of chromosomal abnormalities in eggs increases with age, which may raise the likelihood of pregnancy loss.
Certain health and lifestyle factors: Smoking, obesity, and some chronic medical conditions may affect fertility and the ability to maintain a pregnancy.

However, the underlying cause cannot be determined from symptoms or medical history alone. Some cases remain unexplained even after appropriate investigations. This does not mean that the woman did anything wrong or failed to follow specific instructions.

What Is Recurrent Pregnancy Loss?

The term recurrent pregnancy loss (RPL) describes repeated pregnancy loss. However, the number of losses required before an evaluation is recommended varies among medical guidelines.

European Society of Human Reproduction and Embryology (ESHRE): Defines recurrent pregnancy loss as the loss of two or more pregnancies. The losses do not have to be consecutive.
American Society for Reproductive Medicine (ASRM): Its 2026 update defines recurrent pregnancy loss as two or more pregnancy losses, excluding confirmed ectopic and molar pregnancies.
Royal College of Obstetricians and Gynaecologists (RCOG): Uses a definition of three or more miscarriages but encourages clinicians to consider an evaluation after two losses when an underlying medical cause is suspected.

These differences help explain why doctors may recommend investigations at different stages. Some couples may benefit from an earlier evaluation, particularly when there is a relevant medical history or identifiable risk factor.

Recurrent Pregnancy Loss Tests Recommended by Medical Guidelines

There is no single set of recurrent pregnancy loss tests that is suitable for every couple. The doctor selects the appropriate investigations based on the number of pregnancy losses, the partners' ages, the stage at which the losses occurred, medical and family history, and the results of previous tests.

Some of the main investigations that may be included in the evaluation are:

Antiphospholipid Antibody Tests

Antiphospholipid antibody testing is an important part of evaluating certain cases of recurrent pregnancy loss. It helps identify antiphospholipid syndrome (APS), an acquired autoimmune condition associated with an increased risk of blood clots and pregnancy complications.

The main tests used to assess antiphospholipid antibodies include:

Anticardiolipin test: Measures anticardiolipin antibodies of the IgG and IgM types.
Lupus Anticoagulant test: Detects lupus anticoagulant, an important marker associated with antiphospholipid syndrome.
Anti-Beta-2 Glycoprotein I test: Measures IgG and IgM antibodies against beta-2 glycoprotein I.

A positive result on one test does not automatically confirm antiphospholipid syndrome. Diagnosis requires specific clinical and laboratory criteria. One important laboratory requirement is the persistence of positive antibodies on two tests performed at least 12 weeks apart, taking into account the antibody type, level, and testing method.

For this reason, your doctor may recommend repeating the anticardiolipin test or other antiphospholipid antibody tests after the required interval rather than relying on a single result.

Thyroid Tests (TSH and Anti-TPO)

The thyroid gland plays an important role in regulating metabolism and hormonal functions. Thyroid hormones are also essential during the early stages of pregnancy for fetal development. Untreated hypothyroidism may be associated with an increased risk of pregnancy loss.

A doctor may therefore recommend a group of tests to assess thyroid function, including:

TSH test: Measures thyroid-stimulating hormone and helps assess thyroid activity.
Free T4 test: Measures free thyroxine and may be requested alongside TSH to clarify the nature of a thyroid disorder.
Anti-TPO test: Detects antibodies against thyroid peroxidase and may help identify autoimmune thyroid conditions.

Medical guidelines differ regarding whether thyroid antibodies should be tested routinely in all cases. Some references recommend evaluating them as part of recurrent pregnancy loss investigations, while the 2026 ASRM update focuses on TSH testing according to previous pregnancy outcomes and individual risk factors. It does not recommend routine thyroid antibody testing for every patient without distinction.

Therefore, your doctor determines whether thyroid-related miscarriage tests are necessary based on your symptoms, medical history, and previous results.

Parental Chromosome Testing (Karyotype)

Some cases of pregnancy loss may be associated with structural chromosome changes in one of the partners, such as balanced chromosomal translocations. These changes may not cause noticeable symptoms in the person carrying them, but they can lead to the formation of embryos with chromosomal imbalances, increasing the risk of pregnancy loss.

A karyotype test examines the number and structure of chromosomes in blood cells. A doctor may recommend this test for both partners when there are indications that warrant genetic evaluation.

Situations in which this test may be considered include:

An unbalanced chromosomal abnormality identified in tissue from a previous pregnancy loss.
A family history of certain chromosomal disorders or recurrent pregnancy loss.
No available chromosome analysis from previous pregnancy tissue, alongside risk factors that justify parental evaluation.
Planning certain fertility treatments that require knowledge of the partners' chromosomal status.

However, a karyotype test is not a mandatory routine investigation for every couple experiencing recurrent pregnancy loss. ESHRE and ASRM recommend considering it after an individualized assessment of medical history and risk factors.

Chromosomal testing of pregnancy tissue may also be useful in some cases to determine whether the loss was associated with a chromosomal abnormality in the embryo.

Other Tests Depending on the Individual Case

In addition to the tests mentioned above, a doctor may request further investigations when symptoms or risk factors suggest a specific medical condition.

Examples include:

HbA1c test: May be requested when there is a history of diabetes or risk factors such as obesity or metabolic disorders.
Prolactin test: May be appropriate in cases involving ovulation disorders, unexpected breast milk production, or symptoms suggesting elevated prolactin.
Additional thyroid function tests: Such as Free T4, with other tests added according to TSH results and symptoms.
Pregnancy tissue testing: May help determine whether the loss was associated with an abnormality in the number or structure of chromosomes.
Infection or endometrial investigations: May be requested in selected cases, such as when symptoms or clinical findings suggest chronic endometritis. These tests are not a standard requirement for every patient.

Recurrent pregnancy loss tests need to be guided by a medical evaluation. Performing numerous investigations without a clear indication may lead to confusing results or findings that are not actually related to the cause of pregnancy loss.

Thrombophilia Tests: Why Are They Not Routinely Recommended?

Some people assume that repeated miscarriage necessarily indicates a blood-clotting disorder. As a result, they may request several investigations, such as Protein C, Protein S, and Factor V Leiden tests.

However, medical guidelines do not recommend routine inherited thrombophilia testing for every woman who has experienced recurrent pregnancy loss.

These investigations may include:

Protein C test.
Protein S test.
Antithrombin test.
Factor V Leiden mutation test.
Prothrombin gene mutation test.
MTHFR test.

The reason is that the association between most inherited thrombophilia conditions and recurrent pregnancy loss has not been established strongly enough to consider them direct causes in all cases. Testing without a clear indication may also lead to inaccurate diagnoses or treatments without proven benefits.

ESHRE and ASRM guidelines, along with recent Canadian recommendations, do not recommend routine thrombophilia tests for all cases of recurrent pregnancy loss.

However, a doctor may consider some of these tests if the woman has a personal history of venous blood clots or a strong family history of specific inherited clotting disorders.

It is also important to distinguish inherited thrombophilia from antiphospholipid syndrome. APS is an acquired condition with a recognized association with pregnancy complications. Its evaluation is therefore different from requesting Protein C and Protein S tests without specific indications.

Some laboratory packages may include tests such as protein C and protein S, but their inclusion in a package does not mean they are recommended for every case of recurrent pregnancy loss. It is best to consult your doctor and confirm the package contents with the laboratory before booking.

Non-Laboratory Investigations: Uterine Imaging

The evaluation of recurrent pregnancy loss is not limited to blood tests. Your doctor may also need to assess the shape and cavity of the uterus because certain structural abnormalities can affect embryo implantation or the continuation of pregnancy.

Some of the investigations that may be recommended include:

Transvaginal ultrasound: Helps assess the uterus, endometrium, and ovaries and may identify certain structural abnormalities.
3D ultrasound: Provides a more detailed view of the uterine shape and may help assess congenital abnormalities such as a uterine septum.
Hysterosalpingography (HSG): An X-ray procedure using contrast dye that may be used to assess the uterine cavity and fallopian tubes in selected cases.
Saline infusion sonography: Helps visualize the uterine cavity and identify certain adhesions or endometrial polyps.
Hysteroscopy: May be recommended when the doctor needs to examine the inside of the uterus directly or investigate abnormalities identified through imaging.

The choice of investigation depends on medical history and the results of the initial assessment. Not every woman needs all these procedures. In some cases, combining more than one imaging method may provide a clearer diagnosis.

When Should You Start the Evaluation?

The timing of a recurrent pregnancy loss evaluation depends on the number of pregnancy losses, the woman's age, the stage at which the losses occurred, and her medical and family history.

According to ESHRE and ASRM definitions, an evaluation may be considered after two or more pregnancy losses. RCOG uses a definition of three or more miscarriages but allows earlier evaluation after two losses when an underlying medical cause is suspected.

Once the evaluation begins, couples may go through several steps:

Reviewing medical history: This includes the number of pregnancy losses, when they occurred, any complications, chronic conditions, and medications being used.
Reviewing previous test results: This helps avoid repeating investigations that have already been performed without a medical reason.
Selecting appropriate tests: These may include antiphospholipid antibody tests, thyroid tests, or chromosome testing, depending on the individual's condition.
Assessing the uterus: Appropriate imaging methods may be used when necessary.
Developing a follow-up plan: The doctor determines whether an identified condition requires treatment or whether additional tests are needed before attempting pregnancy again.

It is important to understand that some cases remain unexplained even after a complete evaluation. This does not mean that a successful pregnancy is impossible in the future.

Medical guidelines emphasize providing emotional support and clear information to couples, as pregnancy loss can have a significant psychological impact that deserves attention alongside medical care.

Book Your Recurrent Pregnancy Loss Tests at Nawat Advanced Medical Laboratory

An accurate evaluation of recurrent pregnancy loss begins with selecting tests that match the medical history and clinical assessment, rather than simply performing as many investigations as possible. Following your doctor's recommendations helps avoid unnecessary testing and provides results that can support decisions about the next steps.

Nawat Advanced Medical Laboratory offers a range of medical laboratory services that help assess hormonal and immune indicators, as well as certain clotting and chromosomal factors, according to the available tests and each individual's needs.

If your doctor recommends recurrent pregnancy loss tests, you can contact the laboratory to ask about the package details and available investigations, including the anticardiolipin test, Protein C, Protein S, and other tests, before booking.

Take care of your health and begin your evaluation with clear steps. Book the tests recommended by your doctor at Nawat Advanced Medical Laboratory to obtain laboratory results that can support your medical assessment.

Frequently Asked Questions

1. What is the most common cause of recurrent pregnancy loss?

Chromosomal abnormalities in the embryo are among the most common causes of recurrent pregnancy loss. Nawat Lab can help couples understand relevant laboratory tests as part of a medical evaluation.

2. What is the risk of having a second miscarriage after having one?

After one miscarriage, the risk of another is generally around 20%, although it varies with maternal age and medical history. A specialist can assess individual risk and recommend appropriate tests.

3. What is recurrent pregnancy loss?

Recurrent pregnancy loss refers to experiencing two or more pregnancy losses, although definitions may vary between medical guidelines. Nawat Lab provides laboratory testing that may support the evaluation of possible contributing factors.

4. What are the common causes of miscarriage in early pregnancy?

Early miscarriage is often caused by chromosomal abnormalities in the embryo. Other possible factors include uterine abnormalities, hormonal or thyroid disorders, and certain medical conditions.

5. What habits can cause a miscarriage?

Smoking, alcohol consumption, and using recreational drugs can increase the risk of miscarriage. Maintaining a healthy lifestyle and seeking medical advice before taking medications can support a healthier pregnancy.

Conclusion

Understanding the causes of recurrent pregnancy loss is the first step toward identifying the appropriate investigations and understanding the condition. However, repeated pregnancy loss does not necessarily mean that a healthy pregnancy will not be possible in the future.

Many women go on to have successful pregnancies after experiencing recurrent miscarriages, particularly when their condition is properly evaluated and followed up by a specialist.

Therefore, seek medical evaluation and choose the appropriate tests based on your health history and your doctor's recommendations. You can also contact Nawat Advanced Medical Laboratory to ask about the available investigations that may help complete your evaluation.

Trusted Medical References

For evidence-based information and medical recommendations on recurrent pregnancy loss, consult the following sources:

Recurrent Pregnancy Loss: Causes and the Tests Guidelines Recommend