Cervical Insufficiency: Causes

Pathogenesis (development of disease)

Cervical maturation (maturation of the uterus) is a very complex, active chemical process and a process that is still not fully understood. It is independent of uterine contractions or labor. Simplistically, it resembles a bacterial or abacterial inflammatory reaction (granulocyte and macrophage proliferation/granulocytes belong to the white blood cell group; macrophages are phagocytes). Their release of cytokines (regulatory proteins/protein) and proteases (enzymes/metabolic accelerators that cleave protein) lead to remodeling (softening and loosening) of the cervix. In addition, hormones (progesterone, estrogen), prostaglandins, nitrous oxide and other humoral mediators play an important role, as they also lead to the activation of cytokines, proteases and other enzymes. The cervix consists of 90% connective tissue (collagen, elastin, fibroblasts, proteoglycans, water) and only about 10% muscle. Connective tissue and musculature are densely packed in longitudinal bundles and thus guarantee strength. Already in early pregnancy, softening and loosening takes place due to water retention, and this process continues throughout pregnancy. Then, in late pregnancy, the maturation process has progressed to the point where the cervix (cervix), originally about 4 cm long and rigid (stiff, firm), has shortened and become more or less centered, with a cervix width of 2-3 cm. Labor-assisted further processes cause the cervix to become paper-thin and soft, allowing it to expand to 10 cm and return to a solid state postpartum (“after birth”). In cervical insufficiency, the maturation processes occur prematurely for a variety of reasons, many of which are not understood, so that its holding function is no longer assured.

Etiology (causes)

Biographic causes

  • Genetic burden
    • Genetic diseases
      • Ehlers-Danlos syndrome (EDS) – genetic disorders that are both autosomal dominant and autosomal recessive; heterogeneous group caused by a disorder of collagen synthesis; characterized by increased elasticity of the skin and unusual tearability of the same (habitus of the “rubber man”); organs with connective tissue-rich structures, for example, also the cervix uteri are deficiently formed, the function impaired.

Causes due to disease

Often, the cause of cervical insufficiency is not identifiable. Known causes are:

  • Congenital diseases:
    • Malformations of the Müllerian ducts ( e.g., uterine malformations/malformations of the uterus).
    • Deficiency of:
      • Elastic fibers
      • Collagens
  • Infections:
    • Ascending (ascending) infections.
    • Chorioamnionitis (inflammation of the inner membrane of the egg and the outer layer of the amniotic sacs around the embryo or fetus/unborn child)
    • Urinary tract infections
    • Systemic infections
  • Traumatization of the cervix due to:
    • Rupture (birth injuries, Emmet tear).
    • Conization (surgery on the cervix in which a cone of tissue (cone) is excised from the cervix and then examined microscopically) (the risk of an insufficient cervix is increased if the diameter of the cone is > 10 mm)
    • Overexpansion in:
      • Instrumental abortions
      • Intrauterine (“inside the uterus“) surgeries.