During pregnancy, as the baby grows and gets heavier, it presses on the cervix. This pressure may cause the cervix to start to open before the baby is ready to be born. This condition is called incompetent cervix or weakened cervix, and it may lead to a miscarriage or premature delivery. However, an incompetent cervix happens in only about 1 out of 100 pregnancies.
Carrying your developing baby to full term is the objective of any pregnancy. Most losses during the first trimester are because of chromosomal abnormalities. Second trimester or later losses are often a result of an incompetent cervix.
What causes an incompetent or weakened cervix?
A weakened cervix can be caused by one or more of the following conditions:
- Previous surgery on the cervix
- Damage during a difficult birth
- Malformed cervix or uterus from a birth defect
- Previous trauma to the cervix, such as a D&C (dilation and curettage) from termination or a miscarriage
- DES (Diethylstilbestrol) exposure
How will I know if I have an incompetent cervix?
Incompetent cervix is not routinely checked for during pregnancy and therefore is not usually diagnosed until after a second or third-trimester miscarriage has occurred. Women can be evaluated before pregnancy, or in early pregnancy by ultrasound if they have any of the factors that are potential causes of incompetent cervix. Diagnosis can be made by your physician though a pelvic exam or by an ultrasound. The ultrasound would be used to measure the cervical opening or the length of the cervix.
How often does an incompetent cervix happen?
An incompetent or weakened cervix happens in about 1-2% of pregnancies. Almost 25% of babies miscarried in the second trimester are due to incompetent cervix.
You can’t prevent an incompetent cervix — but the experts at the Mayo Clinic suggest the following tips to help promote a healthy, full-term pregnancy.
- Seek regular prenatal care. Prenatal visits can help your doctor monitor your health and your baby’s health. Mention any signs or symptoms that concern you, even if they seem silly or unimportant.
- Eat a healthy diet. During pregnancy, you’ll need more folic acid, calcium, iron and other essential nutrients. A daily prenatal vitamin — ideally starting a few months before conception — can help fill any dietary gaps.
- Gain weight wisely. Gaining the right amount of weight can support your baby’s health. A weight gain of 25 to 35 pounds (about 11 to 16 kilograms) is often recommended for women who have a healthy weight before pregnancy.
- Avoid risky substances. If you smoke, quit. Alcohol and illegal drugs are off-limits, too. In addition, get your doctor’s OK before taking any medications or supplements — even those available over-the-counter.
What treatment options are available?
The treatment for an incompetent or weakened cervix is a procedure that sews the cervix closed to reinforce the weak cervix. This procedure is called a cerclage and is usually performed between week 14-16 of pregnancy. These sutures will be removed between 36-38 weeks to prevent any problems when you go into labor. Removal of the cerclage does not result in spontaneous delivery of the baby.
A woman would not be eligible for a cerclage if:
- There is increased irritation of the cervix
- The cervix has dilated 4cm
- Membranes have ruptured
Possible complications of cervical cerclage include uterine rupture, maternal hemorrhage, bladder rupture, cervical laceration, preterm labor and premature rupture of the membranes. The likelihood of these risks is very minimal, and most health care providers feel that a cerclage is a life-saving procedure that is worth the possible risks involved.
Want to Know More?
Compiled using information from the following sources:
William’s Obstetrics Twenty-Second Ed. Cunningham, F. Gary, et al, Ch. 9.
Danforth’s Obstetrics and Gynecology Ninth Ed. Scott, James R., et al, Ch. 4.
Incompetent cervix. (2019, July 25). Retrieved from