An incompetent cervix (or cervical weakness) is a condition that is diagnosed when a woman suffers recurrent miscarriage in the mid-stages of pregnancy, usually between weeks 16 and 24.
While the cervix is normally strong enough to manage the pressure of the growing baby, in some women there is a weakness that prevents the cervix from supporting the weight of the foetus, placenta and other fluids. This can be caused by a problem with the anatomy of the cervix; or by previous surgery or injury.
If a woman becomes pregnant again, corrective action can be taken to strengthen the cervix, which involves inserting a stitch known as a cervical clerclage. However, it is not a risk-free procedure and, for this reason, the woman's cervix will be scanned with ultrasound to ensure that a weak cervix is the likely cause of the recurrent miscarriage.
A weak cervix will normally be shorter than a strong cervix, and the ultrasound will determine the length of the cervix. Any undue openings within the cervix can also be identified by the scan.
If the stitch is deemed necessary, this will inserted under a regional or general anaesthetic, between 14 and 16 weeks of pregnancy. It will be removed at 37 weeks of pregnancy.
While the stitch can be very effective, it does carry risk factors which an obstetrician will discuss before the surgery goes ahead. These include infection or bleeding, both of which can trigger late miscarriage or premature labour.