Repeat miscarriage: 5 main causes (and tests to be carried out)

Recurrent miscarriage is defined as the occurrence of three or more consecutive involuntary terminations of pregnancy before the 22nd week of gestation, the risk of which occurs is greater in the first months of pregnancy and increases with advancing age.

There are several causes that may be at the origin of the occurrence of successive miscarriages, therefore, an assessment of the couple must be carried out, gynecological and genetic tests must be carried out and an evaluation of the family and clinical history must be carried out, in order to understand what is at the root of the problem.

The occurrence of an abortion is a traumatic experience, which can lead to symptoms of depression and anxiety and, therefore, women who suffer from repeated miscarriages should also be properly monitored by a psychologist.

Some of the most common causes of recurrent miscarriage are:

1. Genetic changes

Fetal chromosomal abnormalities are the most common cause of miscarriage before 10 weeks of pregnancy and the probability of occurring increases with maternal age. The most common errors are trisomy, polyploidy and monosomy of the X chromosome.

The cytogenetic analysis examination must be carried out on products of conception from the third consecutive loss. If this examination reveals anomalies, a karyotype analysis must be carried out using peripheral blood from both members of the couple.

2. Anatomical anomalies

Uterine anomalies, such as Müllerian malformations, fibroids, polyps and uterine synechiae, may also be associated with recurrent miscarriage. Learn how to identify changes in the uterus.

All women suffering from recurrent miscarriage must undergo an examination of the uterine cavity, using pelvic ultrasound with a 2D or 3D transvaginal probe and hysterosalpingography, which can be complemented with endoscopy.

3. Endocrine or metabolic changes

Some of the endocrine or metabolic changes that may be the cause of recurrent miscarriage are:

• Diabetes: In some cases, women with uncontrolled diabetes have an elevated risk of fetal loss and malformation. However, if diabetes mellitus is well controlled, it is not considered a risk factor for miscarriage;
• Thyroid dysfunction: As in the case of diabetes, women with uncontrolled thyroid function disorders also have an increased risk of suffering a miscarriage;
• Changes in prolactin: Prolactin is a hormone of great importance for endometrial maturation. Therefore, if this hormone is too high or too low, the risk of miscarriage is also increased;
• Polycystic ovary syndrome: Polycystic ovarian syndrome has been associated with an increased risk of miscarriage, but it is not yet known exactly what mechanism is involved. Learn how to identify and treat polycystic ovary;
• Obesity: Obesity is associated with a significantly increased risk of spontaneous pregnancy loss in the first trimester;
• Changes in the luteal phase and progesterone deficiency: A functional corpus luteum is essential for successful implantation and for maintaining the pregnancy in its initial phase, due to its important role in the production of progesterone. Thus, changes in the production of this hormone can also lead to the occurrence of a spontaneous abortion.

Find out what the corpus luteum is and its relationship with pregnancy.

4. Thrombophilia

Thrombophilias are diseases that cause changes in blood clotting and increase the chance of forming blood clots and causing thrombosis, which can prevent the embryo from implanting in the uterus or cause miscarriages. Thrombophilias are generally not detected in common blood tests.

Find out how to deal with thrombophilia during pregnancy.

5. Immunological causes

During pregnancy, the embryo is considered a foreign body by the mother’s organism, which is genetically different. To do this, the maternal immune system has to adapt so as not to reject the embryo. However, in some cases, this does not happen, leading to miscarriages or difficulty getting pregnant.

There is an exam called cross-match, which investigates the presence of antibodies against paternal lymphocytes in the mother’s blood. To carry out this test, blood samples are taken from the father and mother and, in the laboratory, a cross-test is carried out between the two, to identify the presence of antibodies.

Furthermore, alcohol and tobacco consumption may also be associated with recurrent miscarriage, as they negatively influence pregnancy.

Although in most cases the causes of recurrent miscarriage can be determined, there are situations that remain unexplained.