What is Cervical Insufficiency?
We speak of "cervical insufficiency" when - due to a structural or functional defect, congenital or acquired - the cervix is unable to support a pregnancy until its term. In other words, the cervix presents a structure weak and not very toned, which does not allow it to remain closed for the duration of the pregnancy.
Risks for Pregnancy
During gestation, the uterine cervix (also known as the neck of the uterus) represents a precious mechanical support that prevents the premature exit of the fetus. The pressure exerted by the latter, which increases with growth, can lead to excessive dilation of the incontinent cervix even in the absence of uterine contractions.
Cervical insufficiency - also known as cervical insufficiency or cervical incompetence - is therefore a cause of premature birth, which in turn is currently the main cause of neonatal mortality and morbidity.
Incidence
Due to the absence of clear diagnostic identification criteria, the incidence of cervical incompetence is not clearly established. However, on the basis of the available data, it seems to affect about 1% of the obstetric population; in other words, one in 100 pregnant women has this problem.
Causes
In most cases, cervical insufficiency is an idiopathic condition, therefore not attributable to precise causes. Cervical incompetence, which arises without apparent cause, therefore tends to remain unknown, at least until the first pregnancy, when it can result in series consequences for the fetus: abortion in the second trimester or premature birth.
Among the recognized causes of cervical incompetence there are both congenital factors, however of rare observation, and acquired factors, such as previous obstetric trauma or gynecological interventions.
intrauterine exposure to diethylstilbestrol (DES *);
Mullerian anomalies;
connective tissue anomalies;
hypoplasia;
longitudinal hypertrophy.
Previous obstetric factors: intrapartum cervical lacerations; excessive forced dilation of the neck to voluntarily end the pregnancy; breech extraction; multiparity; application of forceps
Previous gynecological interventions: conization of the portio; electrosurgical excisional procedures, instrumental dilation of the cervical canal.
Table.1: Causes of cervical incompetence (Centaro A, Rondinelli M. "The treatment of" cervical-isthmic incompetence. "Ann Obstet Gynecol 1973; 94: 3-27).
Conization
Conization consists in the removal of a small cone of tissue from the neck of the uterus, by means of electric loops, lasers or scalpels, for diagnostic and therapeutic purposes, in particular in the treatment of non-invasive cervical carcinomas or preneoplastic lesions.
Although it is a conservative intervention, which preserves the "functional and structural integrity of the uterus, guaranteeing the possibility of future pregnancies, there is an" association between conization and an increased risk of preterm birth, mediated by an "acquired and post-cervical incompetence. surgical. The risk is the higher the greater the height of the removed cone, which in turn is proportional to the extent of the abnormal tissue detected during the colposcopy.
How dangerous is it?
Cervico-isthmic incompetence is responsible for 16% of all spontaneous abortions, usually in the second trimester, and for many cases of prolapse and / or premature rupture of membranes resulting in preterm delivery of a low-weight fetus. following table, the risk of pre-term birth is important, but it can be contained by an early diagnosis.
Among the causes of cervical incompetence, the short (or short if you prefer) cervix stands out, which in turn recognizes various causes. This condition is diagnosed by transvaginal ultrasound, which evaluates the length of the neck of the uterus by comparing it with a cut-off value that varies, depending on the sources, from 2 to 2.5 centimeters. In other words, it arises diagnosis of short cervix when the cervix is less than 2.5 or 2 centimeters long. Several studies have shown that the chances of a pre-term birth increase as the length of the cervix decreases.
* measured between the 16th and 18th week in women with previous preterm birth
Diagnosis
The pre-pregnancy diagnosis of cervical incompetence is mainly based on a more or less suggestive anamnesis due to the presence of the following risk factors:
- History of > 2 miscarriages in the second trimester (excluding those due to onset of preterm labor or placental abruption)
- Stories of spontaneous interruptions at increasingly early gestational ages
- History of asymptomatic cervical dilation up to 4-6 centimeters
- History of cervical trauma caused by:
- Conization
- Intrapartum cervical lacerations
- Excessive, forced, dilation of the neck during IVG (Voluntary Termination of Pregnancy)
and on the possible presence, during the inspection of the cervix, of defects such as, for example, conspicuous results of previous obstetric and / or surgical traumas.
The parameters to be evaluated by transvaginal ultrasound to diagnose cervical incompetence during pregnancy are as follows:
- length of the uterine cervix;
- characteristics (width, length, percentage) of the "possible" funneling "(dilation of the proximal tract of the cervical canal which takes on a wedge-shaped appearance)
Treatment
In case of cervical insufficiency the patient is considered at risk of premature birth. There are two treatment options:
- non-surgical: bed rest, abstention from physical activity (by remaining standing, the force of gravity that pushes down, combined with the poor seal of the cervix, would determine the premature expulsion of the fetus), supplement with progesterone, use of a pessary vaginal, "short therapy with indomethacin" and tocolytic therapy
- surgical: transvaginal cervical cerclage (CTV) according to the Shirodkar or McDonald technique, transabdominal cervical cerclage (CTA). This operation, to be performed at a gestational age generally less than 24 weeks, involves applying a synthetic fabric tape to the neck of the uterus, to be removed before childbirth, in order to strengthen the cervix and increase continence. The preventive effectiveness of this intervention is questioned by various specialists, so cerclage is generally reserved only for women with a history of premature births or specific indications.
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