Isthmico-cervical insufficiency

Cervical insufficiency is the inability of the cervix to support the fetus in the absence of uterine contractions or labor (painless dilation of the cervix) due to a functional or structural defect. It is the ripening of the cervix that occurs far ahead of schedule. Cervical insufficiency is rarely a separate and clearly defined clinical entity, but is only part of a larger and more complex syndrome of spontaneous preterm labor. [ 1 ]

The incidence of cervical insufficiency in patients with habitual miscarriage is 13–20%. Pathognomonic signs of cervical insufficiency include painless shortening and subsequent opening of the cervix in the second trimester of pregnancy, accompanied by prolapse of the amniotic sac and/or rupture of amniotic fluid, ending in miscarriage or, in the third trimester, the birth of a premature baby.

Anatomical causes of habitual miscarriage also include isthmic-cervical insufficiency, which is recognized as the most common etiological factor in termination of pregnancy in the second trimester. [ 2 ]

• History of cervical trauma (post-traumatic cervical insufficiency):
  • damage to the cervix during childbirth (ruptures that are not surgically repaired; operative deliveries through the natural birth canal - obstetric forceps, delivery of a large fetus, a fetus in breech presentation, fetal-destroying operations, etc.);
  • invasive methods of treating cervical pathology (conization, amputation of the cervix);
  • artificial abortions, late-term termination of pregnancy.
• Congenital anomalies in the development of the uterus (congenital isthmic-cervical insufficiency).
• Functional disorders (functional isthmic-cervical insufficiency) - hyperandrogenism, connective tissue dysplasia, increased levels of relaxin in the blood serum (noted in multiple pregnancies, ovulation induction with gonadotropins).
• Increased stress on the cervix during pregnancy - multiple pregnancy, polyhydramnios, large fetus.
• Anamnestic indications of minor, rapid abortions in the second trimester or early premature birth. Methods for assessing the condition of the cervix outside of pregnancy, as a rule, do not provide complete information on the probability of developing isthmic-cervical insufficiency during pregnancy. Such an assessment is possible only in case of post-traumatic isthmic-cervical insufficiency, accompanied by gross violations of the anatomical structure of the cervix. In this situation, HSG is performed on the 18th-20th day of the menstrual cycle to determine the condition of the internal os. If the internal os is dilated by more than 6-8 mm, this is regarded as an unfavorable prognostic sign.

The question of the advisability of cervical plastic surgery is decided jointly with a gynecological surgeon, taking into account the patient's medical history (number of late pregnancy terminations, ineffectiveness of therapy with other methods, including cervical suturing during pregnancy), the condition of the cervix, and the possibilities of surgical correction in each specific case. Cervical plastic surgery outside of pregnancy is most often performed according to Yeltsov-Strelkov. Plastic surgery performed outside of pregnancy does not exclude surgical correction of the cervix during pregnancy. When performing plastic surgery outside of pregnancy, delivery is possible only by cesarean section due to the risk of cervical rupture with transition to the lower uterine segment.

Preparation for pregnancy in patients with habitual miscarriage and isthmic-cervical insufficiency should begin with the treatment of chronic endometritis and normalization of the vaginal microflora. Due to the fact that the locking function of the cervix is impaired, the uterine cavity becomes infected with opportunistic flora and/or other microorganisms (chlamydial, ureaplasma, mycoplasma infections). An individual selection of antibacterial drugs is carried out, followed by an assessment of the effectiveness of treatment based on the results of bacteriological examination, PCR, and microscopy of vaginal discharge.

Symptoms of cervical insufficiency are as follows:

• a feeling of pressure, distension, stabbing pain in the vagina;
• discomfort in the lower abdomen and lower back;
• mucous discharge from the vagina, may be streaked with blood; scanty bloody discharge from the vagina.

It is important to remember that isthmic-cervical insufficiency can be asymptomatic.

In foreign literature, ultrasound signs of isthmic-cervical insufficiency are described, obtained during examination with a transvaginal sensor, including with load tests (test with pressure on the fundus of the uterus, cough test, positional test when the patient stands up).

Measuring the length of the cervix using ultrasound data allows us to identify a group at increased risk of developing premature birth.

Up to 20 weeks of pregnancy, the length of the cervix is very variable and cannot serve as a criterion for the occurrence of premature birth in the future. However, pronounced dynamics of the state of the cervix in a particular patient (shortening, opening of the internal os) indicates isthmic-cervical insufficiency.

At 24–28 weeks, the average length of the cervix is 45–35 mm, at 32 weeks and more – 35–30 mm. Shortening of the cervix to 25 mm or less at 20–30 weeks is a risk factor for premature birth.

• Anamnestic data (minor pain late miscarriage) or rapid premature birth, with each subsequent pregnancy at an earlier gestational age.
• Prolapse of the amniotic sac into the cervical canal as a result of a previous pregnancy.
• Ultrasound data - shortening of the cervix by less than 25–20 mm and dilation of the internal os or cervical canal.
• Softening and shortening of the vaginal portion of the cervix when examined in speculums and during vaginal examination. [ 3 ] Recent studies have shown that suturing the cervix in women with isthmic-cervical insufficiency reduces the incidence of very early and early premature births up to 33 weeks of pregnancy. At the same time, it was noted that such patients require the use of tocolytic drugs, hospitalization, and antibacterial therapy, in contrast to patients who were prescribed only bed rest. [ 4 ]

• Placental abruption.
• Fetal growth retardation.
• Multiple pregnancy.
• Preeclampsia.
• Premature rupture of membranes.
• Premature birth.

In high-risk patients (those with habitual miscarriage in the second trimester), cervical monitoring should be performed from 12 weeks of pregnancy if posttraumatic cervical insufficiency is suspected, from 16 weeks if functional cervical insufficiency is suspected, at least at two-week intervals, and weekly if necessary. Monitoring includes examination of the cervix in speculums, vaginal examination, and, if necessary, ultrasound assessment of the length of the cervix and the condition of the internal os. [ 5 ], [ 6 ], [ 7 ]

Surgical correction during pregnancy in case of developed isthmic-cervical insufficiency in combination with bed rest is more effective than bed rest alone.

The most common methods of surgical correction of isthmic-cervical insufficiency are the application of sutures according to Shirodkar, McDonald in modifications, and the U-shaped suture according to Lyubimova.

For surgical correction of isthmic-cervical insufficiency the following conditions are necessary:

• a living fetus without developmental defects;
• pregnancy period no more than 25 weeks;
• whole amniotic sac;
• normal uterine tone;
• no signs of chorioamnionitis;
• absence of vulvovaginitis;
• absence of bloody discharge from the genital tract.

Postoperative management includes the administration of antispasmodics (drotaverine hydrochloride at a dose of 40 mg 2 times a day intramuscularly), antibacterial therapy, and, if necessary (with increased uterine tone), tocolytic therapy.

During pregnancy management after cervical suturing, it is necessary to conduct bacterioscopy of vaginal discharge and examination of the condition of the sutures on the cervix every 2 weeks; if pathological discharge from the genital tract appears, examination is performed more often, taking into account the indications. Indications for removing sutures from the cervix:

• pregnancy period - 37 weeks;
• at any stage of pregnancy, in case of leakage or outpouring of amniotic fluid, bloody discharge from the uterine cavity, cutting of sutures (formation of a fistula), the beginning of regular labor.

In complex cases, when the vaginal portion of the cervix is so small that it is not possible to suture it transvaginally (after amputation of the cervix), sutures are applied transabdominally using laparoscopic access (the world literature describes about 30 such operations during pregnancy).