Overview

Cervical insufficiency is also known as cervical incompetence or weak cervix. It is a functional or structural defect of the cervix that causes painless dilation during the second trimester and preterm delivery. It is an inability to hold the foetus during pregnancy, even where there are no contractions from the uterus. This condition that leads to preterm loss of pregnancy rarely occurs in isolation but is part of a more complex chain of events. It occurs in approximately 1 in 100 pregnancies.¹

The cervix, also known as the neck of the womb,  is an important organ in the female reproductive anatomy.It is a muscular, small canal located at the base of the uterus that connects to the vagina and acts as a gatekeeper that remains closed during pregnancy to protect the growing foetus. The cervix also plays an important role during labour allowing the baby to leave the uterus. It is also important in other female reproductive processes and functions  like menstruation, fertility, conception, and uterine protection. 

During pregnancy, the cervix undergoes many changes in preparation for labour and the birth of the baby, i.e. it gets shorter, softens, and opens. In cervical insufficiency, these changes happen a lot sooner than required and the cervix begins to open, causing the foetus to be expelled from the uterus.

Causes of cervical insufficiency

Cervical insufficiency may be acquired or congenital. For congenital cervical insufficiency, the woman is born with the condition, due to genetic predisposition or structural abnormalities. For example, a genetic problem affecting a type of protein called collagen can affect the structure of the cervix. For acquired cervical insufficiency, previous trauma, surgeries, inflammation, or infections may be contributing factors. The most common acquired cause is cervical trauma. As mentioned previous surgery, a procedure on the cervix or a cervical tear during a previous labour can also cause this. Exposure to a certain hormonal drug called diethylstilbesterol while in the womb. This medication was given up until 1971 as it was thought to prevent miscarriage. However, it has now been linked to issues with the reproductive organs and premature birth in foetuses that were exposed to it.² 

Symptoms of cervical insufficiency

There are often no symptoms of an early opening of the cervix. However, a few signs may indicate the presence of cervical insufficiency and prompt the diagnosis. This is made in three different settings:

• Women who suddenly present the onset of symptoms and signs of cervical insufficiency 
• Women with a history of miscarriage in the second trimester of a previous pregnancy
• Women who have had preterm deliveries before 37 weeks of pregnancy
• Women with vaginal ultrasound findings that are consistent with cervical incompetence

These signs will not exist in women carrying their first pregnancies. Other signs to look out for, especially in the second trimester include pelvic pain, backache, unusual cramping, light bleeding, vaginal discharge that increases in volume and changes in colour starting from pale pink.

If the above symptoms are noticed during pregnancy, regular prenatal care may spot this insufficiency of the cervix early and prevent the loss of the baby or preterm birth. 

Risk factors

Any woman can be at risk of developing cervical insufficiency. However, women with the following may be at a higher risk.

• An irregularly shaped cervix or uterus
• Previous miscarriage in the second trimester
• Injured cervix or uterus during previous pregnancy or delivery
• Previous procedure on the cervix
• A genetic disorder (like Ehlers-Danlos syndrome) that may cause weakness of the cervix and lead to cervical insufficiency

Research has also shown that people of African origin and those carrying multiple pregnancies are also at a higher risk of developing this condition. 

Diagnosis of cervical insufficiency

Cervical insufficiency can be difficult to diagnose, and it can be found only during pregnancy. A diagnosis is given if a woman has:

• A history of painless cervix dilation and previous second-trimester delivery
• Advanced cervical softening and thinning of the cervix before 24 weeks of pregnancy. This can be accompanied by vaginal bleeding, infection or ruptured amniotic membrane

For women at high risk of cervix insufficiency, diagnosis in the second trimester may include:

• A transvaginal ultrasound used to measure the cervix towards the start of the second trimester. A cervix that is dilated 2cm or above, measuring less than 25mm in length with the bag of water protruding into the vagina is given a diagnosis of cervical insufficiency³ 
• A pelvic exam can also be done to check if the amniotic sac can be felt through the opening. If this occurs, it is called a prolapsed foetal membrane
• Lab tests are done by carrying out vaginal swabs to check for signs of preterm labour. This method checks for the presence of substances like foetal fibronectin that are only present in the vagina when the woman is at an increased risk of preterm labour. These tests are also done to check for infections

The diagnosis of cervical insufficiency is often made based on history and retrospectively, after poor birth outcomes. The woman’s medical history is also assessed to identify risk factors.

Treatment options

There are non-surgical and surgical methods to treat cervical insufficiency and delay the delivery for as long as possible. The non-surgical approaches include bed and pelvic rest, activity restriction, progesterone and vaginal pessary. 

• Bed rest and activity restriction can mean anything from no sex or difficult activity to complete immobility
• Progesterone can be prescribed as an injection or vaginal suppository to reduce the risk or reoccurrence of a spontaneous preterm birth by preventing contractions
• Vaginal pessary is a newer alternative to progesterone. It is a small ring designed to wrap around the cervix and close it to hold the uterus in place. This may reduce the pressure on the cervix

It is important to note that more research is required to show the potential benefits of the methods listed above. 

The surgical approach is called a cervical cerclage or a cervical stitch. Cervical cerclage is a strong stitch that closes the opening of the cervix and is removed once the baby is at term (between 36 to 38 weeks). This procedure is done transvaginally as a McDonald or a Shiradkor procedure or transabdominal is the transvaginal cerclage is difficult to perform.³ The McDonald procedure is the most used cerclage and is performed using a permanent suture around the cervix. The Shiradkor technique involves the dissection of the bladder to place the suture higher up in the vagina.⁴

For women at risk of premature births, a cervical cerclage can be used as a preventive measure. However, not every pregnant woman at risk of premature delivery is eligible for this procedure. For example, women carrying multiple pregnancies are advised against it and require further consultations with their healthcare provider for other suitable procedures.

Prognosis and complications

Post-surgery, cervical cerclage may lead to complications such as uterine contractions, haemorrhage, lesions in the cervix, cervical lacerations, severe infections, high fever, and preterm premature rupture of membranes (PPROM), amongst other postoperative problems.⁵ This procedure may also have neonatal risks that may lead to contractions or bleeding that can cause a miscarriage or preterm labour. Some cerclages like the abdominal one are left in place and the baby must therefore be delivered via caesarean section. These complications must therefore be adequately balanced against the benefit of the procedure.

Prevention strategies

Cervical insufficiency cannot be prevented. However, to increase the chances of having a healthy pregnancy and carrying the pregnancy to term, the following should be considered.

• Regular prenatal care and check-ups during pregnancy is vital for monitoring mother and baby’s health
• Eating a healthy diet is essential during pregnancy as essential nutrients like folic acid, and calcium are required for health growth and development of the baby
• Gaining a healthy weight during pregnancy to support mother and baby’s health
• Staying off toxic substances including alcohol, illegal drugs, cigarettes

Women who have had cervix insufficiency in one pregnancy are at risk of pregnancy loss or preterm delivery in subsequent pregnancies and should therefore talk to their healthcare provider if considering having another baby.

Summary

Cervical insufficiency poses a significant risk to pregnant women, leading to preterm deliveries and potential pregnancy loss. Understanding the structural and functional aspects of the cervix is crucial in recognizing the symptoms and risk factors associated with this condition. While diagnosis during pregnancy can be challenging, early detection through regular prenatal care and specific diagnostic methods can help mitigate the risks.

The causes of cervical insufficiency, whether congenital or acquired, underscore the importance of identifying and addressing risk factors, such as previous traumas or genetic predispositions. Prompt recognition of symptoms, such as pelvic pain and unusual bleeding, provides an opportunity for intervention, potentially preventing preterm births.

Effective diagnosis involves a combination of medical history, physical examinations, and specialized tests, like transvaginal ultrasound and pelvic exams. However, the difficulty in early detection highlights the need for continued research and advancements in diagnostic tools.

Treatment options, ranging from non-surgical approaches like bed rest and progesterone to surgical interventions such as cervical cerclage, offer strategies to delay delivery and improve outcomes. Nevertheless, the potential complications associated with these treatments necessitate careful consideration of individual cases.

While cervical insufficiency cannot be prevented, proactive measures such as regular prenatal care, maintaining a healthy lifestyle, and avoiding harmful substances contribute to healthier pregnancies. Women with a history of cervical insufficiency should engage in open discussions with healthcare providers to assess risks and explore suitable preventive measures for subsequent pregnancies.