What is incompetent cervix?
Cervical incompetence is a common cause of repeated pregnancy loss.
In a typical pregnancy, the cervix remains tightly closed until it is time to give birth. The cervix then begins to soften, shorten, and dilate (open) in preparation for birth under hormonal influence.
If you have cervical incompetence, your cervix may undergo these changes (softening, shortening, and dilating) well before you give birth. When this occurs, the cervix may not be strong enough to support the growing fetus, putting the pregnancy at risk. Most women who miscarry as a result of cervical incompetence lose the pregnancy around 20 weeks.
The cause of cervical incompetence is unknown, but it is thought to be caused by a physical weakness in the woman’s cervix, which makes it susceptible to giving way as the baby grows larger and heavier, putting increased pressure on the cervix as the pregnancy progresses. Both genetic and environmental factors are thought to play a role.
Risk factors for cervical incompetence
The length of the cervix is affected by several factors, including:
- Over-distended uterus (a term meaning that the uterus has been stretched too far)
- Bleeding during pregnancy
- Inflamed uterine lining
- Certain infections
Risk factors for cervical incompetence include:
- Previous losses:
- Women who have miscarried twice or more in the second trimester appear to be at a higher risk for cervical insufficiency.
- Collagen disorders:
- Ehlers–Danlos syndrome and Marfan’s syndrome, which affect collagen (a protein in the body that gives skin and tissues strength and elasticity), can increase risk.
- Gynecologic history:
- Cervical trauma:
- Some surgical procedures used to treat cervical abnormalities caused by an abnormal Papanicolaou smear can result in cervical insufficiency.
- Other procedures, such as dilation and curettage, may be linked to cervical insufficiency.
- Congenital conditions:
- An incompetent cervix can be caused by uterine abnormalities and genetic disorders that affect the body’s connective tissues.
- Furthermore, prenatal exposure to synthetic estrogen has been linked to cervical insufficiency.
- Ethnicity:
- Cervical insufficiency appears to be more common in African-American women, although the reason needs more research.
- Increased maternal age:
- Because of aging, the muscles surrounding the cervix begin to lose elasticity, which may contribute to the cervix’s weakening.
- Other causes:
- Being pregnant with more than one baby (twins or triplets)
- Birth trauma
- A previous forceps delivery
Women may be classified as high or low risk for cervical shortening or incompetence based on the factors listed above, and this will influence how they are treated.
High-risk women
- History of a previous painless miscarriage between 12 and 24 weeks
- Premature delivery
- Surgery to the cervix
If your doctor determines that you are at high risk of having a short or weak cervix based on your medical, surgical, and obstetric history, she may recommend:
- As part of your first-trimester screening, you will have a transvaginal ultrasound to determine the length of your cervix.
- If they are diagnosed with an abnormal cervix, they may be offered medication or a surgical procedure to treat it.
- They may also require additional ultrasounds to determine the length of the cervix, which is most commonly done at 18 to 20 weeks and again at 24 weeks. Scans may also be required at other times.
Low-risk women
- There is no prior history of early delivery, but an ultrasound or vaginal examination demonstrates a short cervix in their current pregnancy.
Women who do not have any risk factors for cervical incompetence or a short cervix are advised to have:
- At 18 to 20 weeks gestation, a transvaginal ultrasound is used to determine the length of the cervix.
- If the cervix is larger than 25 mm, no further ultrasound is required.
- If the cervix is shorter than 25 mm, treatment with medications or a surgical procedure may be discussed.
- Patients may also require additional ultrasounds to measure the length of the cervix, which would most commonly occur every two weeks until 24 to 28 weeks.
An incompetent cervix can endanger your pregnancy, especially in the second trimester. Premature birth and unexpected pregnancy loss are the most serious consequences of cervical insufficiency.
If cervical incompetence is detected early, doctors will closely monitor the fetus and cervix to prevent premature birth and miscarriage. Premature birth can result in a variety of neonatal risks and birth injuries, including brain damage to infants.