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Synonyms: Premature ripening of the cervix;

Definition: Condition in which the cervix fails to retain the conceptus during pregnancy. Cervix length less than 25 mm.

History: Lash described in 1950 cervical cerclage the treatment of cervical incompetence^[1].

Prevalence: Affects 1% of pregnant patients^[2].

Etiology:

• Idiopathic (most)

• Congenital disorders (congenital mullerian duct abnormalities^[3],
• DES exposure in utero^[4]),
• Connective tissue disorder (Ehlers-Danlos syndrome^[5])
• Surgical trauma (conization, resulting in substantial loss of connective tissue) or traumatic damage to de structural integrity of the cervix (repeated cervical dilatation associated with termination of pregnancies).

Pathogenesis: The function of the cervix during pregnancy depends on the regulations of connective tissue metabolism. Collagen^[6]is the principal component in the cervical matrix, others are proteoaminoglycans, elastin and glycoproteins like fibronectin^[7]. The biochemical events implicated in the cervical ripening are: decrease in total collagen content, increase in collagen solubility^[8] and increase in collagenolytic activity. Inflammatory response^[9] are involved too (Interleukins : IL1, IL8, tumor necrosis factor a, prostaglandins, nitric oxide^[10]), matrix degrading enzymes (matrix metalloproteinases) and sex steroids hormones (17 b-estradiol induces ripening, estrogen stimulates collagen degradation in vitro, progesterone blocks the estrogen induced collagenolysis in vitro, progesterone receptor antagonist induces cervical ripening in the first trimester).

Sonographic findings:

• Funneling of the cervix with the changes in forms T, Y, V, U (correlation between the length of the cervix and the changes in the cervical internal os).

The T, Y, U, V (Trust Your Vaginal Ultrasound) stages and the bulging membranes.

There are also two identical video clip of an incompetent cervix. The first is a 0.5 MB and the second is 1.2 MB. They only differ by the compression utilized.

• Cervix length < 25 mm
• Protrusion of the membranes.
• Presence of fetal parts in the cervix or vagina.

Implications for targeted examinations: Extended exam for 15-20 minutes visualizing the cervix shows spontaneous changes of the cervix^[12]. Cervical stress test at 15-24 weeks (increasing transfundal intrauterine pressure while monitoring cervical length and the appearance of funneling^[13]) is recommended for the patients with

• history of painless dilatation followed by fetal expulsion in the second trimester

• conization
• uterine malformations (uterus unicornis, uterus bicornis, uterus didelphys)
• cervical trauma (conization)
• history of spontaneous and therapeutic abortions
• preterm birth before 32 weeks .

2 images of the same cervix, 20 seconds apart, without and with applying pressure:

Ultrasonography is the principal modality of the diagnosis during pregnancy (transabdominal, transperineal or transvaginal), MRI appearance of the cervical incompetence may demonstrate a higher degree of soft tissue contrast than ultrasonography^[14].

Differential diagnosis: Other causes of preterm labor (PROM, chorioamnionitis , uterine contractility) .

Management: In patients at risk for pregnancy loss, placement of cervical cerclages in response to sonographic detected shortening of the endocervical canal length is an acceptable alternative to the use of elective cerclage^[15].

References

^[1] Lash,AF, Lash, SR. Habitual abortion; the incompetent internal os of the cervix. Am J Obstet Gynecol, 1950; 59:68.

^[2] Callen, Ultrasonography in Obstetrics and Gynecology. Saunders. 4^th  Edition, 577-596.

^[3] Abramovici, H, Faktor, JH, Pascal,B. Congenital uterine malformations as indication for cervical suture (cerclage) in habitual abortion and premature delivery. Int J Fertil. 1983; 28:161.

^[4] Singer, MS, Hochman, M. Incompetent cervix in hormone-exposed offspring. Obstet Gynecol 1978; 51:625.

^[5] Rudd,NL, Nimrod, C, Holbrook, KA, et al. Pregnancy complications in type IV Ehlers-Danlos syndrome. Lancet, 1983; 8:50.

^[6] Yu, SY, Tozzi, CA, Babiarz,J. et al. Collagen changes in rat cervix pregnancy-polarized light microscopic and electron microscopic studies. PSEBM. 1995 ;209:360.

^[7] Uldbjerg, N, Forman, A, Peterson, LK et al . Biochemical changes of the uterus and cervix during pregnancy. In: Reece, EA , Hobbins, J, Mahoney, MJ et al eds. Medicine of the fetus and of the mother. Philadelphia: JB Lippincott; 1992:849.

^[8] Leppert, PC, Proliferation and apoptosis of fibroblast and smooth nuscle cells in rat uterine cervix throughout gestations and the effect of the antiprogesterone onapristone. Am J Obstet Gynecol, 1998 178:713.

^[9] Liggins,GC Cervical ripening as an inflamatory reaction. In: Ellwood, DA Anderson ABM, eds. The cervix in pregnancy and Labour:  Clinical and Biochemical Investigations. Edinburgh: Churchill-Livingstone; 1981.

^[10] Thompson, AJ, Lunan CB, Cameron, A.D., et al. Nitric oxide donors induce ripening of the human cervix: A randomized controlled trial. Br J Obstet Gynecol.1997; 104: 1054.

^[11] Zilianti, M, et al. J Ultrasound Med. 1995; 14:719-724.

^[12] Parulekar, SG, kiwi, R. Dynamic incompetent cervix uteri: sonographic observations. J. Ultrasound Med. (1988) 7:481

^[13] Guzman , ER, Pisatowski, DM, Vintzileos AM et al. A comparison of ultrasonographically  detected cervical changes in response to transfundal pressure, coughing and standing in predicying cervical incompetence. Am J Obstet Gynecol 1997; 177:660.

^[14] Maldjian C., Adam, R., Pelosi, M., Pelosi, M. 3rd. Mag. Reson. Imaging (1999 Nov; 17 (9): 1399-402).

^[15] Guzman, ER, Forster, JK Vintzileos, AM Ananth CV, Walters, C, Gipson, K Pregnacy outcomes in woman treated with elective versus ultrasound-indicated cervical cerclage. Ultras. Obst. Gynecol, 1998 Nov, 12 (5): 301-3.