Causes of Miscarriage

According to the Japanese Society of Obstetrics and Gynecology, a “miscarriage” is defined as a pregnancy that finishes before the 22nd week (the time at which the baby cannot live outside the mother’s womb).
There are also statistics that say around 15% of pregnancies lead to miscarriages, and this is possible to happen to anyone.
From this number, about 80% of the miscarriages are early stage miscarriages occurring by the 12th week of pregnancy.

As for the cause of miscarriages, it is often unknown, but as for those causes that have become clear they can be divided into fetal factors and maternal factors.
Chromosomal anomalies are usually the contributor for fetal factors.
Even if many aneuploid embryos are implanted, the development will discontinue.
If the chromosomes of a fetus that was actually miscarried are examined, 65% have aneuploidy.
Also, if the mother’s age is over 35, the fetuses found with chromosomal anomalies increases to 74%.

As causes on the maternal side, there’s immunity and anomalies with the clotting factor, along with anomalies of the uterus.
As an anomaly of immunity the antiphospholipid antibody syndrome, and as an anomaly of the clotting factor, the decline of the 12th factor of blood clotting is said to be connected.
As for anomalies of the uterus, endometriosis causes inflammation, and the tissues of the inner membrane will come together to form “Uterine lumen adhesion”, and other “uterine morphological anomalies”, such as the said sectioned uterus with partitions inside the uterus, and a bicornuate uterus in which the shape of the uterus has been constricted to that of a heart-like shape.

After a miscarriage, there are people who think “the cause was perhaps in me” and look back on their lifestyle and work, blaming themselves.
However, the cause of a miscarriage is hardly ever due to the pregnant woman’s lifestyle or job.

Repeated Miscarriages and Habitual Miscarriages

When there are 2 or more miscarriages one after the other it is called a “repeated miscarriage”, and if it is 3 or more times in a row it is called, “habitual miscarriage”.
At the same time, even after getting pregnant and the baby doesn’t grow and there’s a condition of repeated miscarriages and still births, this is called, “non-developing syndrome”, a very severe condition of infertility.
Most of the causes of miscarriages are related to chromosomal anomalies of the fetus, and it is a natural miscarriage due to natural selection.
However, with a repeated miscarriage of 3 or more times, it will be necessary to test to see whether or not there are risk factors that make it easy for miscarriages to happen. Even in cases where there are risk factors, it is not that 100% will be miscarried.
In risk factors of the non-development syndrome, either the paternal side or the maternal side has chromosomal constructional aneuploidy.
In this case, the couple are completely healthy, but when they produce their oocytes and sperm (cases of meiosis where the chromosomes become half), there will be an occurrence of an excess or deficiency in chromosomes, and it will be the cause of miscarriage.
Additionally, as risk factors on the maternal side, there are those such as uterus malformation, endocrine abnormalities, clotting anomalies, and older maternal age.

Risk Factors of Habitual Miscarriage

  • Couple’s chromosomal anomalies(80% of miscarriages of early stage)
  • Uterus malformations(formation abnormalities like bicornuate uterus and partitioned uterus, also uterine inflammation, cervical incompetence, and intrauterine adhesion disease)
  • Endocrine imbalances(luteal function failure, hyperprolactinemia, hyper-thyroid gland⁄ hypothyroidism, and diabetes)
  • Blood clotting abnormalities(12th factor deficiency, protein S deficiency, protein C deficiency, etc)
  • Immunological reactions (Antiphospholipid antibody syndrome, auto-immune disease, and homogenous immune anomalies)
  • Infection(Chlamydia, Syphilis)

We are providing the general information about Preimplantation Genetic Diagnosis.