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.
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 a 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.
What is the treatment for a weakened cervix?
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.
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.
American Pregnancy Association, http://www.americanpregnancy.org