Pregnancy loss is quite common. It is estimated that about 10% to 20% of pregnancies end in miscarriage, although the actual figure may be higher as miscarriages often occur even before the pregnancy is known. 

In most cases, the cause of pregnancy loss is embryonic: the embryo does not develop properly or is non-viable, leading to the woman’s body ending the pregnancy naturally. Doctors often consider this to be a one-off event and do not give it much importance. But what if it happens more than once? Are there other possible causes? What protocol is usually followed in these cases? 

According to Dr Núria Murcia, a fertility specialist at Dexeus Mujer in Manresa and Barcelona, “After two consecutive miscarriages, it is advisable to see an expert, both because of the emotional impact and to undergo tests to help find the cause or rule out any medical condition”. 

Older women face a higher risk of pregnancy loss because as age increases, egg quality declines, which leads to a higher rate of chromosomal abnormalities in embryos —one of the most common causes of miscarriage. However, young women may also experience recurrent pregnancy loss, “so each case must be assessed individually,” says Dr Murcia. 

What can cause recurrent pregnancy loss? 

“Typically, what we do is conduct tests to check if there is any specific issue hindering embryonic development and pregnancy progression,” explains Dr Núria Murcia. It is crucial to assess the patient’s age, her medical history and that of her male partner (if she has one), her family history, etc., as the causes can vary significantly: 

  • The most common cause is an embryonic problem. This accounts for more than 50% of miscarriages. 
  • Chromosomal abnormalities in the patient or her male partner. These abnormalities may go unnoticed, but lead to embryos with alterations that are not compatible with life. 
  • Congenital uterine malformations. The cause may be an undetected uterine problem at a structural level, which may interfere with proper embryo implantation and development. 
  • Fibroids. Not all fibroids entail a risk of miscarriage; it depends on their location, size and number. 
  • Endocrine disorders. Properly treated thyroid gland dysfunctions are not a risk factor, but it is essential to have good control of endocrine disorders, as if left untreated, they can increase the likelihood of miscarriage. 
  • Obesity and low weight are other factors that may increase the risk of miscarriage. 
  • Antiphospholipid syndrome. This autoimmune disorder causes blood clots and thrombosis, which can lead to problems with blood flow and circulation. This condition can be treated with anticoagulant drugs. 

As you can see, this is a rather complex issue, with no clear guidelines, because establishing a cause-effect relationship can be challenging. “My advice to patients in these cases is to seek and follow the guidance of a specialist. Having two or even three recurrent miscarriages does not mean that a couple cannot achieve a successful pregnancy, and having more or fewer tests does not always lead to finding a definite cause. That is why professional experience and studying and assessing each particular case are the best guides to find solutions and reduce the risk of another pregnancy loss,” concludes Dr Murcia. 

What are the recommended tests? 
To find out the potential cause of recurrent pregnancy loss, your gynaecologist may recommend undergoing some of the following tests: 

  • Study of the uterine cavity through a 3D transvaginal ultrasound, a hysteroscopy or an MRI. The aim is to rule out possible physical or structural issues. 
  • Karyotype. This genetic test examines the complete set of chromosomes in an individual. 
  • Endocrine tests. If uterine problems and chromosomal abnormal abnormalities are ruled out, the cause may be endocrine-related, possibly linked to a thyroid gland dysfunction. 
  • Endometrial tests. There are specific tests to assess endometrial microbiota, although they are not recommended systematically, only in certain cases. 
  • Thrombophilia testing. It is particularly important to assess antiphospholipid syndrome, as mentioned above. An expanded coagulation study may be considered based on a personal or family history of thrombosis or venous thromboembolism. 
  • Seminogram. If your partner is male, the doctor may recommend a semen analysis, which shows sperm morphology and motility and measures its concentration. 
  • Sperm FISH and DNA fragmentation test. FISH is a technique that analyses the chromosomal content of spermatozoa. A high degree of sperm DNA fragmentation may be the reason for repeated miscarriages. 
  • Preimplantation genetic testing (PGT). This is advisable when undergoing an IVF treatment. This technique studies embryos to detect any anomalies or chromosomal abnormalities. It allows selecting embryos without abnormalities to be transferred to the uterus in order to reduce the risk of miscarriage.