What causes Recurrent Miscarriage or Habitual Abortion?

Recurrent miscarriage refers to a sequence of three or more consecutive spontaneous abortions before 20 weeks, affecting 1% of all women of reproductive age.

A recurrent miscarriage may be primary or secondary (having previous viable birth).

If you are experiencing recurrent miscarriages, it doesn’t mean you will not have any viable pregnancy. There are chances of having a successful pregnancy with a healthy baby after many recurrent miscarriages. Understandably, pregnancy loss is a very distressing experience for every woman. But don’t lose hope.

Causes of Recurrent Miscarriage

The exact cause of recurrent miscarriage is unknown but certain factors are responsible for it. Let you know about each one. These are described below-

Genetic chromosomal factors

Parental chromosomal abnormalities is a proven cause of recurrent miscarriage. There is a 50% of chromosomal imbalance in any form of spontaneous miscarriage. However, the chance of a successful pregnancy even without any treatment is 40-50 %.

Endocrine and metabolic factors

There is an increased incidence of early pregnancy failure in diabetic mothers. If you are a diabetic then you need diabetes treatment to have a successful pregnancy.

Hypothyroidism (the thyroid gland doesn’t produce enough thyroid hormone) also lead to miscarriage.

In early pregnancy, if there is less production of progesterone due to luteal phase defect leads to miscarriage.


When there is an infection in the genital tract, it may lead to spontaneous abortion but it may not cause recurrent miscarriage. Transplacental ( infection can cross the placental barrier to reach the fetus) infection can occur with most microorganisms. Syphilis is an infection that can cause abortion even after 20 weeks.

Inherited thrombophilia

Thrombophilia can be defined as a predisposition to form clots inappropriately. This condition can pass from parents to their children. It can cause both early and late miscarriages due to the formation of clots in the vessels which supply blood to the baby.

Anatomical defects

Anatomical defects are responsible for 10 to 15% of recurrent abortions. It may be congenital (defect in the Mullerian duct fusion) or acquired.

1. Uterine anomalies, 15%

Congenital anomalies may include –

  • Septate or double uterus
  • Unicornuate uterus
  • Bicornuate uterus
Septate uterus (left) and Double uterus (right)
Septate uterus (left) and Double uterus (right)

Acquired anomalies may include –

  • Intrauterine adhesions
  • Uterine fibroids
  • Endometriosis

2. Cervical incompetence, 20%

It is an important cause of pregnancy loss in the second trimester. It is due to the congenital (rare) or acquired weakness of the internal os and whole cervix. The retentive power of the cervix may be impaired by D + C operation, induced abortions and vaginal operative delivery through an undilated cervix.

Immunological factors

When there is a failure in immune adaptation during early pregnancy then recurrent abortions may occur.


Despite the various factors mentioned above, it is difficult to identify the exact cause of abortion in the majority of cases. The risk of miscarriage increases with increased women age.

When you are having recurrent miscarriages, you need to undergo a complete examination to rule out the cause so that the appropriate treatment can be instituted. There is a possibility of having a successful pregnancy even after recurrent miscarriages.


In the above post, we discussed the various causes of recurrent miscarriages. The factors responsible are genetic chromosomal, endocrine and metabolic, infections, inherited thrombophilia, anatomical defects, immunological and unexplained factors. There are chances of having a successful pregnancy even after recurrent miscarriages.

Thank you all!!! Hope you find this useful.

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