Cervical Incompetence
Cervical Incompetence

Cervical incompetence is an uncommon condition where the cervix shortens or opens in a pregnancy before it is time to do so. Unlike during a labour, where the opening of the cervix is usually associated with pain, in the condition of incompetent cervix, there may not be any pain.  This most commonly occurs in weeks 12-20 of a pregnancy resulting in miscarriage or may occur later in the pregnancy with early delivery of the baby who may be too small to survive.  The diagnosis is usually only made once a pregnancy has occurred and there has been an early delivery resulting in a miscarriage or premature baby.   There are treatment options available if you have been diagnosed with this problem that are designed to strengthen the cervix and carry the pregnancy to (as close to) term as possible.

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The word ‘cervix’ means neck and in the uterus, the cervix describes the ‘neck’ or narrowest portion of the uterus. The cervix is a unique part of the uterus that needs to be long and strong through the majority of the pregnancy but needs to soften (‘ripen’), shorten and open (dilate) when labour starts. This is a very complex situation and we still do not completely understand how the cervix works.

Risk Factors

There are a number of factors that put the cervix at risk of shortening or becoming incompetent in a pregnancy.  These include:

  1. An abnormally shaped uterus
  2. Previous surgery to the cervix (such as a cone biopsy or LLETZ procedure for abnormal cells of the cervix)
  3. Multiple dilations of the cervix (D&C)
  4. Inherited conditions that cause weakening of the cervix

When the problem of cervical incompetence first occurs, there may be few warning symptoms until the membranes rupture or there is pressure in the pelvis and delivery of the baby is inevitable.  There may be an increase in vaginal discharge noted, which is pink or blood stained. Other symptoms may include pressure in the back or vagina, with period like pain occurring very infrequently.  When the problem of vaginal shortening or incompetence is suspected, it may be diagnosed with an internal ultrasound scan through the vagina (‘transvaginal ultrasound’).  If the cervix length measures 25 mm or less, then it is considered to be short.  A direct vaginal examination using a speculum (the instrument used when you are having a Pap smear) may demonstrate an open cervix and the fluid filled sac that is usually within the uterus around the baby may be seen coming through the cervix.

Figure 1. A typical transvaginal ultrasound image of a longitudinal section through a short cervix.

Cervix Short

Women may be considered high risk or low risk for cervical shortening or incompetence and this would affect the way that they are treated.

  1. High risk women are those with a history of a previous painless miscarriage between 12-24 weeks; a premature delivery thought to be due to cervical incompetence; surgery to the cervix
  2. Low risk women are those with no previous history of an early delivery, but are demonstrated to have a short cervix by ultrasound or a vaginal examination in their current pregnancy

High risk women

For women who are determined to be high risk of having a short or weak cervix based on you past medical, surgical and obstetric history, your Alana doctor will recommend that you have a transvaginal ultrasound to measure the length of your cervix as part of your first trimester screening. Should this be considered to be short, you may be offered treatment by medications or a surgical procedure (see below). You will also need to have further ultrasounds that would measure the length of the cervix and this would most commonly occur at 18-20 weeks and again at 24 weeks.  Scans at other times may also be required.

Low risk women

Women without any risk factors for cervical incompetence or short cervix are recommended to have a transvaginal ultrasound to measure the length of the cervix at 18-20 weeks gestation. If the cervix measures more than 25 mm no further ultrasound is needed. If the length of the cervix is less than 25 mm we will discuss treatment by medications or a surgical procedure (see below). You will also need to have further ultrasounds that would measure the length of the cervix and this would most commonly occur each 2 weeks until 24-28 weeks.

Treatments for cervical incompetence

There are two options for this condition – a surgical procedure and medication delivered by a pessary into the vagina.

Cervical cerclage:  This is a surgical procedure that aims to close the cervix with a stitch and to keep it closed until term or as close to term as possible.  A piece of synthetic tape or suture is placed around or through the cervix, increasing its strength. The procedure may be performed vaginally, laparoscopially or abdominally and this will depend on the length of the cervix and whether it is an elective or an emergency procedure.  The two most common types of cerclage are called Shirodkar or McDonald after the doctors who performed them first.

With a Shirodkar suture, a vaginal approach is used and an incision is made in the front of the cervix and the bladder is pushed back and also at the back of the cervix and then a tape or a tube is placed as close to the top of the cervix as possible.  The skin is then closed over the tape or tube.  A caesarean delivery is usually recommended and the tape may remain in place for future pregnancies.

With the McDonald cerclage, the stitch is placed through the main body of the cervix without pushing back the bladder or bowel and is the more commonly performed suture when the cervix is very short or the membranes and sac may be seen coming through the cervix.   This is called an emergency stitch.

Figure 2.  This is a figure showing the usual place for a stitch to be located to keep the cervix closed

Cervix with Suture

For either cerclage, the procedure needs to be performed in hospital under a general anaesthetic so that you are maximally relaxed.  After you are asleep, your legs are placed in stirrups so that the cervix may be clearly and easily seen.  The top of the cervix is identified and the stitch is placed according to the methods described above.  If the stitch is being placed as an emergency, you will be placed in a head down position, particularly if the membranes and fluid sac is coming through the cervix as this is a high-risk suture and the membranes may be damaged.

Other risks include infection of the cervix or possibly in the sac around the pregnancy (called chorioamnionitis – see below), bleeding, trauma to the cervix or surrounding tissues such as the bladder or bowel.  It is important to note that this is a high-risk procedure and may result in miscarriage.

Infection inside the uterus (chorioamnionitis) may be an important cause of cervical shortening, rather than always being a result of a procedure to close the cervix.   If you are having a cerclage procedure, your Alana doctor will perform vaginal swabs and blood tests to look for any sign of infection and to determine which bacteria or other microbe is responsible for the infection.   You will be commenced on antibiotics and it is essential that you continue on these for as long as directed.

If there are symptoms or signs of severe infection, then it may in fact be dangerous to place a stitch as this may lead to severe infection for you. If a stitch is placed in the cervix and your waters break (rupture of membranes) after its placement then it must be removed, owing to the high risk of infection.  Your Alana doctor will discuss future treatments.

Studies have shown that the placement of cervical sutures may reduce the risk of premature delivery (before 34 weeks) by 35%. This is an approximate figure only and is dependent whether is stitch is placed electively or as an emergency and your individual circumstances.  After a stitch is placed, you will require individualised and frequent follow-up that we will discuss with you.

Medical treatment:  A second option for treatment of a short cervix is by using the hormonal treatment progesterone. For women who are recommended to have this treatment option, a vaginal pessary containing 200 mg of progesterone is inserted each night before bed.  It is common to have a vaginal discharge when using this medication owing to the outer coating of the pessary and there may be mild vaginal irritation.  It is also possible to use the suppositories rectally if this occurs.

Long-term use of progesterone in pregnancy is considered very safe and there are no increased major birth defects for babies born to women using progesterone in this manner.  For male babies born to women using progesterone, there is a mild increase in a condition called hypospadias where the urethra doesn’t end in the centre of the penis.

Which treatment should I have and when?

If you are diagnosed with a short cervix, the choice of treatment needs to be tailored to a variety of factors and your Alana doctor will direct you as to the most appropriate treatment for your particular circumstances.  No matter which treatment is used, we recommend close observation with an ultrasound to assess the length of the cervix to be performed each 2 weeks at Alana.   The number of weeks of pregnancy is also important, since both cervical cerclage and vaginal progesterone are reasonable for women presenting with a short or weak cervix until 24 weeks. After this gestation, a baby will most likely survive if born, and placement of a suture is considered a very high-risk procedure. In this situation, vaginal progesterone pessary treatment is the safer option.

What happens if no treatment works?

Research has shown that if the cervix measures less than 10 mm in length then neither cerclage nor progesterone may be effective in preventing delivery.   If this occurs prior to 24 weeks, your baby may not survive and our aim is to help you through this difficult time and focus what we can do for future pregnancies.

If we see on ultrasound scan that the cervix is shortening despite a cerclage or progesterone treatment, there are options available to prepare for a premature delivery after 24 weeks gestation. Our aim is to optimise the condition of your baby so they have the best chance of survival.   We will discuss all aspects of care and intervention with you and may recommend a course of steroid injections given to you 24 hours apart.  Steroids work by going through the mothers system into the baby and improving lung and bowel function.  It also reduces the risk of bleeding inside your baby’s head.

It has long been held that complete bed rest to take the pressure off the cervix may help to reduce the risks associated with early delivery in women with a short cervix.  Research does not support this view for most women, however in certain circumstances you may be advised to reduce your activity or even to have bed rest and this would be discussed with you on an individual basis.

At Alana we will guide you through the decision-making for what is the best and most appropriate treatment for your unique circumstances.  We recognise that this is a very difficult and anxiety-provoking time for you and your family and will stand by you providing information, skills and compassion to help you through this difficult time. Please contact Alana is you wish to discuss your individual circumstances at a consultation with one of our specialists.