What is cervical incompetence?
Cervical incompetence is when the cervix, for various reasons, is weak and therefore begins to dilate too early in the pregnancy. This complications classically painless dilation of the cervix. Usually this progression begins to happen from 20-26 weeks. A woman is usually without symptoms. At most she may just feel pressure when the process has become advanced. Usually she does not feel contractions until she is very dilated, and therefore often women present with a very dilated cervix in early pregnancy, or even delivering.
Why is the cervix weak?
The cervix is made up of collagen. It has been shown that women with cervical insufficiency have decreased amounts of collagen. Sometimes the cervix may be weak because of other procedures, or surgical manipulation, of the cervix as below. Local inflammation, and other hormonal factors likely play a role as well.
What are the risk factors for cervical incompetence?
• History of loss between 20-26 weeks. This may indicate a congenitally weak cervix.
• Trauma to the cervix. This would include history of surgery, abnormal Paps with cone or LEEP procedures, and multiple terminations or d & c's.
• An abnormally shaped uterus, bicorneate uterus or uterine didelphys for example.
• Multiple gestation, probably from overdistension.
Since there are not good symptoms of incompetent cervix, women with these risks should be watched very closely for incompetent cervix in early pregnancy.
What are the Signs of Incompetent Cervix?
It can be very hard, if not impossible to recognize incompetent cervix in early pregnancy. Sometimes, the only signs a woman may have is pelvic pressure. Increased discharge or spotting may indicate the early cervical changes, but many normal pregnant women also have these problems.
Often cervical incompetence is simply picked up on routine ultrasound. The best way to evaluate the cervix is with a vaginal ultrasound. This will allow your doctor to look at the length and shape of your cervix. If a cervix is shorter than 2.0 cm early in the pregnancy, this is a red flag for incompetence. If it is starting to internally dilate, or "funnel", this is also a red flag for incompetence. Often a cervix is short, but functions very well. In this case a woman can progress quite far in the pregnancy. However, it is impossible to image the function of the cervix, which is really what is more important. Therefore, the patient will likely be placed on bedrest and watched very closely. Because the signs of incompetent cervix are so vague, we include a look at the cervix, at least abdominally, with all ultrasounds. Transvaginal ultrasound should be performed in women at higher risk.
Is there a treatment for cervical incompetence?
This may be the most debated area in obstetrics! Bedrest and limiting the physical pressure on your cervix with no heaving lifting, etc. probably helps delay delivery. If a cervix is found to be short, less that 2- 2.5 cm, early in the pregnancy, a woman will likely be advised to go on bedrest with limited activity.
Recent studies show promise for a new treatment of short cervix. This treatment is progesterone suppositories. (see http://www.AskAnOB.com/recentadvances/preventpretermdelivery.html).
Many physicians will consider a "cerclage". A cervical cerclage is a stitch that encircles the cervix at the opening of the uterus. This stitch helps to close the cervix to prevent further dilation and prolapse of the bag of water through the cervical os. It makes perfect sense that a cervical cerclage should be effective in preventing further dilation of the weak cervix, and we often have patients that appear to greatly benefit from having this procedure. However, in multiple studies (see below) the stitch has not been shown to be any more effective than bedrest in preventing early delivery of the pregnancy. In fact some of the data shows cerclage may actually increase infection rates. Therefore it is not a "quick fix" and should be used in very select patients. Most physicians will only put in stitches up to 23-24 weeks, or before fetal viability (survivability).
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Overview of Major Studies of Cerclage:
Woman at risk because of history:
1. MRC Medical Research Council/ Royal College of Obstetricians and Gynaecologist multicentre randomised trial of cervical cerclage. 1993
Studied 1292 women in many countries. Cerclage was compared with bedrest in women felt to be at risk because of history of early delivery or cervical surgery. Preterm delivery rate at less than 33 weeks was 28%. There were fewer early deliveries in the cerclage group. However, cerclage increased the rate of hospitalization and maternal fevers.
2. Rush et al. A randomized controlled trial of cervical cerclage in women at high risk of spontaneous preterm delivery. 1984.
Studied 194 women felt to be high risk for early preterm delivery. Cervical cerclage did not improve outcome or prolong pregnancy. Patients with cerclage spent more time hospitalized, had more fevers, and were more likely to receive drugs to stop labor
3. Lazar et. al. Multicentred controlled trial of cervical cerclage in women at moderate risk of preterm delivery. 1984.
Studied 504 women at moderate risk of preterm delivery. No significant differences with respect to prolongation of pregnancy in women with cerclage over bedrest alone. There was more hospitalizations in women with cerclage.
Woman at risk because of short cervix and/or history:
1. Olatunbosun et al. Emergency cerclage compared with bedrest for advanced cervical dilation in pregnancy. 1995.
Studied 43 women with a cervix over 4 cm dilated. 22 women underwent emergency cerclage. 15 women underwent bedrest alone. Cerclage resulted in longer pregnancy prolongation over bedrest alone. In addition, birthweights were higher in the cerclage group.
2. Berghella et al. Cerclage for short cervix on ultrasonography: Meta-analysis of trials. 2005.
Reviewed all pertinent studies (four studies) to date on this topic. This included over 600 patients with a short cervix. Preterm birth at less than 35 weeks occurred in 29% of women with cerclage, 35% of women without a cervical cerclage. This was not a statistically significant difference. However, women with singleton pregnancies (one baby) did appear to benefit significantly. This was especially true if the patient also had a history of a preterm delivery. If a cerclage was placed in twins, however, the rate of preterm delivery was actually higher.
3. Althuisus et al. Cervical incompetence prevention randomized cerclage trial: emergency cerclage with bedrest versus bedrest alone. 2003.
Studied 23 women with advanced cervical dilation. These women had a dilated cervix with expsed membranes. Thirteen women received a cerclage, 10 received bedrest alone. The mean gestational age at inclusion was 22 weeks. If a woman received a cerclage, the mean gestational age at delivery was 29.9 weeks. With bedrest alone, the mean gestational age at delivery was 25.9 weeks. This was a significant difference.
4. Daskalakis et al. Management of cervical insufficiency and bulging fetal membranes. 2006.
Studied 29 women with advanced cervical dilation up to 26 weeks. Women who received cerclage prolonged pregnancy a mean of 8.8 weeks. Without a cervical cerclage, pregnancy prolongation was a mean of 3.1 weeks. Birthweights were also higher in the cerclage group. Neonatal Intensive Care Unit admission was higher in the bedrest alone group.
5. Pereira et al. Expectant management compared with physical examination-indicated cerclage in selected women with a dilated cervix at 14- 26 weeks gestation. (From the EM-PEC international cohort study). 2007
Studied 225 women, 152 who received cerclage. Cerclage placement was associated with prolongation of pregnancy. It as also associated with increased neonatal survival, birthweight over 1500 gm, and delivery > 28 weeks.
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