The incidence of three or more consecutive spontaneous abortions is called habitual abortion, and its incidence is as high as 10%-20%. Cervical incompetence is a very important factor leading to late-stage habitual abortion.
I. Cervical incompetence
Cervical incompetence is a term used to describe the inability of the cervix to maintain a pregnancy to term due to anatomical or functional defects in the absence of contractions. The typical clinical presentation is painless dilatation of the cervix in mid- to late pregnancy with bulging of the gestational sac into the vagina and subsequent delivery of the immature fetus. Cervical insufficiency is the main cause of miscarriage and preterm delivery in the middle and late stages of pregnancy and recurs if left uncorrected. Cervical cerclage is now a common treatment for cervical insufficiency and has improved perinatal outcomes to some extent.
Miscarriage and preterm delivery due to cervical insufficiency account for about 0.05-1.8% of all pregnancies, with about 20% of miscarriages occurring at 13-27 weeks of gestation and 80% of preterm deliveries occurring at 28-37 weeks of gestation.
II. High-risk factors.
The frequency of future cervical insufficiency is high in baby girls born to pregnant women taking menestrol, which reaches the fetus through the placenta and affects the composition of the collagen fibers of the cervix. It is worth noting that the opening of the uterus is more than 5 cm wide during cesarean delivery with a low incision in the lower uterine segment, which may cause cervical insufficiency in the future.
Third, etiology.
It mainly includes cervical dysplasia and cervical injury due to trauma.
There is no real sphincter at the endocervix, which is composed of epithelium, glands, connective tissue and smooth muscle, of which connective tissue accounts for 85% and smooth muscle accounts for 15%. The connective tissue is mainly composed of collagen fibers, which are highly elastic and function as a sphincter for the pregnant cervix. Congenital cervical dysplasia is mainly due to the reduction of collagen fibers that make up the cervix, the elongation and expansion of the uterine isthmus in the middle of pregnancy to form the lower part of the uterus, the gradual shortening of the cervix due to the amniotic sac and the gravity of the fetus, and the opening of the cervix without abdominal pain, followed by late miscarriage and preterm delivery. In addition, estrogen exposure during the fetal period of the pregnant woman herself and Mullerian duct malformation are also high risk factors for cervical insufficiency.
Surgical trauma is seen in cervical lacerations from childbirth, rapid cervical dilation, and after cervical conization or LEEP. Injury to the cervical canal results in impaired integrity of the cervical sphincter. Whether cervical insufficiency is caused after conization is related to the length of the cervical canal after conization.
4. Diagnosis of cervical insufficiency
The diagnosis of cervical insufficiency is mainly based on the history of recurrent spontaneous abortion or preterm delivery in the middle of pregnancy, and transvaginal ultrasound measurement of the width of the endocervix and the length of the cervix. In contrast, iodine oil imaging of the uterine tubes and probing the width of the endocervix with a non-pregnant luteal phase cervical dilator are methods that have not undergone rigorous scientific validation.
1. Medical history: With a clear history of cervical injury or recurrent spontaneous abortion in the middle of pregnancy, miscarriage mostly occurs in the same gestational week, and there is no obvious abdominal pain and contractions, and labor progresses rapidly. Before the onset of the disease, the patient often felt only pelvic pressure and increased mucus secretion.
In some patients, although there is a history of multiple midtrimester spontaneous abortions or preterm deliveries, careful history taking usually begins with premature rupture of membranes, followed by regular abdominal pain hours or even days later, even requiring oxytocin to induce contractions. The cause of miscarriage or preterm labor in such patients may be premature rupture of membranes and not cervical insufficiency.
2. Physical examination: In the middle of pregnancy, there is no obvious abdominal pain but the endocervical opening is more than 2 cm and the cervical canal is shortened and softened, especially the softening is more important. Sometimes the amniotic sac has protruded outside the cervical os.
3. Ultrasonography.
Transvaginal ultrasound is currently a more reliable diagnostic method. In cases of suspected cervical insufficiency, the cervical changes can be monitored continuously at 2-week intervals starting at 14-16 weeks.
In normal pregnancies, the length of the cervix and the width of the internal opening are relatively stable, with a cervical length of 35-40 mm and an internal opening width of 20 mm before 30 weeks of gestation, and a cervical funnel rate: funnel length/(funnel length + length of the closed part of the cervix), after 30 weeks the cervix starts to shorten progressively. In cases of cervical insufficiency, cervical shortening or funnel formation begins at 18-22 weeks.
4. Ultrasound diagnosis: cervical length <25 mm, inner opening width >15 mm, cervical leakage rate >25%.
It is worth noting that in 5% of patients, the cervical length changes only after 5-10 minutes of the examination. The cervical stress test helps to diagnose cervical insufficiency at an early stage: if the cervical structure changes after pressure is applied to the fundus of the uterus or the pregnant woman stands for a period of time, the possibility of cervical insufficiency is high if the cervix is significantly shortened or the endocervix shows a funnel shape.
5. Clinical diagnostic criteria: in the middle of pregnancy without contractions: ① shortening of the cervical canal, which is generally considered to be more than 30% compared to normal pregnancy; ② canal opening of the cervical canal, which is more than 10 mm from the external to the internal cervical cavity; ③ opening of the internal cervical cavity, which is wedge-shaped or funnel-shaped, with a bulging amniotic sac and a residual cervical canal less than 30 mm long. The length of the cervix ≤20 mm or the width of the internal opening >15 mm at 15-20 weeks of gestation; ④ the No. 8 Hegar dilator can be passed through the cervical opening without resistance.
V. Cervical cerclage for cervical insufficiency.
By ligating the cervix, the flaccid endocervix is reinforced and the duration of pregnancy is prolonged, thus preventing the occurrence of preterm labor and late abortion and improving the survival rate of perinatal babies.
Indications for surgery: All cervical incompetence is an indication for cervical ligation, but those with normal cervical length by vaginal ultrasound do not need medical intervention unless there is a history of multiple preterm abortions.
2. Contraindications to surgery: chorioamnionitis, premature rupture of membranes, fetal malformation, fetal death in utero, and active uterine bleeding are absolute contraindications to cervical cerclage. Anterior placenta and fetal growth restriction are relative contraindications to cervical cerclage.
3, timing of surgery: generally chosen at 14-28 weeks, also can be chosen 4 weeks before the last miscarriage weeks, special circumstances can be relaxed to 36 weeks before.
4.Pre-operative preparation: First of all, ultrasound examination should be completed to exclude fetal malformation, routine examination including blood, urine routine, coagulation function, virus series, electrocardiogram, fetal amniotic fluid chromosome and cervical discharge examination if necessary, good vaginal cleanliness and no bloody discharge from the cervix are necessary for successful surgery.
5.Cycloplasty classification: selective cervical cerclage, emergency cervical cerclage and emergency cervical cerclage Selective cervical cerclage: prophylactic cervical cerclage that has been clearly diagnosed before pregnancy, early pregnancy, before the cervical changes at 13-16 weeks of gestation, for those with more than three unexplained miscarriages or premature births in mid-term pregnancy.
Emergency cervical cerclage: in cases where changes such as shortening of the cervix or formation of the funnel have occurred but the opening of the uterus has not yet opened. Patients usually have back pain, irregular contractions, spotty vaginal bleeding or mucous discharge.
Emergency cervical cerclage: Emergency cervical cerclage is feasible when the opening of the uterus is wide, with or without fetal membrane bulge, but there should be no contractions or contractions have been effectively suppressed.
6.Cervical cerclage method
① Transvaginal cervical cerclage.
U-shaped suture of the cervix.
② Transabdominal cervical cerclage.
Transabdominal uterine isthmus ligation is rarely used and is usually used for congenital cervical dysplasia, severe cervical laceration or scarring, and failure of previous transvaginal cervical ligation. The bladder is separated from the lower uterine segment and polyester sutures are placed around the upper part of the cervix for subsequent delivery by cesarean section. The annuloplasty can be done laparoscopically.
7. Cervical cerclage precautions
① The plane of cervical cerclage should be comparable to the level of the inner cervical opening.
②The operation should be performed to minimize the stimulation of the cervix and not to penetrate the mucosal layer of the cervix.
(iii) The ligature should be as loose or tight as the ectocervix can accommodate a fingertip.
8.Postoperative management
① postoperative routine suppression of contractions: choose magnesium sulfate, ampoule, progesterone, etc. to suppress contractions. Note that the rate of static magnesium sulfate should be more than 2g/hour.
②Postoperative antibiotics to prevent infection.
③Pay attention to bed rest after surgery and elevate the hips if necessary. Prohibit activities that increase abdominal pressure and physical labor.
④Keep the vulva clean and give iodophor scrubbing if there is more vaginal discharge, and apply suppositories if necessary.
⑤ Keep the bowels open.
(6) Ultrasound examination every 3 weeks after surgery to check the shortening and dilatation of the uterine orifice. (7) If there is dilatation of the cervix and other conditions in the postoperative follow-up, a second cervical cerclage operation will be performed above the first ligature line after a full assessment of the possible amniotic cavity infection, premature rupture of the fetal membranes and potential risk factors brought about by the second ligature operation.
9. Time of suture removal: It is generally believed that sutures can be removed during cesarean section if there is an indication for cesarean delivery. Sutures can be removed at 37-38 weeks of gestation for those who plan to deliver via vagina. If there is premature rupture of membranes, contractions, vaginal bleeding and signs of infection, the sutures should be removed promptly.
10.Surgical complications: cervical cerclage is an invasive treatment method, bleeding, infection and premature rupture of membranes may occur after surgery; obstructed labor, cervical tearing and postpartum bleeding may also occur during labor.