Cervical Weakness and miscarriage

Cervical weakness also known as cervical incompetence is a known anatomical cause of miscarriage and pregnancy loss may be recurrent.

The cervix (or neck of the womb) is normally strong enough to remain closed throughout the course of pregnancy, in spite of the ever-increasing size and weight of the womb contents. In fact, even at term, hormonal changes have to take place to facilitate cervical thinning and dilatation and therefore labor.

When there is cervical incompetence, the cervix is anatomically weak, causing the womb to lose its contents - around mid-pregnancy. Typically, miscarriage caused by an incompetent cervix occurs between sixteen and twenty-four weeks of gestation.

Causes of cervical incompetence (weakness)

The known causes of cervical incompetence include previous therapeutic dilatation of the cervix (D&C), which could be done during surgical termination of pregnancy.

Cone biopsy is increasingly uncommon. This is a mode of diagnosis and treatment for a severely abnormal cervical smear.

Both these procedures may subsequently lead to cervical incompetence but this is quite uncommon. Most gynecologists will avoid forcibly dilating the cervix whenever possible, especially since alternatives are available, in many cases.

Miscarriage due to cervical incompetence

In the majority of cases of cervical incompetence, miscarriage will occur without so much as a warning. The classic presentation is a gush of fluid as the membranes of the gestational sac break. This follows a silent opening of the weakened cervix.

Once the "waters" have broken, the process is virtually irreversible. The woman will proceed to miscarry in a matter of hours.

Correcting cervical incompetence

If a diagnosis of an incompetent cervix is made following such a miscarriage, remedial action has to wait until the woman has conceived again. Corrective action is taken after fourteen weeks, when the possibility of spontaneous miscarriage from other causes has receded to negligible, and a scan has verified that the fetus and placenta are growing normally. Fourteen weeks is also just before entering the danger period of miscarriage caused by cervical incompetence.

The commonly used method is to insert a special suture in the weakened cervix to close it and hold it in that closed state. The procedure is called "cervical cerclage" and, depending on how the suture is made, names for the procedure such as Shirodikar and Macdonald will be used.

This is in most cases done vaginally, and the suture is subsequently removed at thirty-eight weeks of gestation, ready for labor.

The insertion of the stitch is done in theatre under a general anaesthetic. Many obstetricians will advise a hospital stay of at least a day, for complete rest and observation. There is a small risk that the action of inserting the suture could trigger a miscarriage, hence this precaution.

Removal of the suture is straightforward and does not require going to theatre or an anaesthetic. If the woman is going to have a cesarean delivery, the suture could be left in place especially if she is planning to conceive again in the future. Experts hold different views on this.