Weakness of the cervix, which may result in a late miscarriage
- Age, genetics, and lifestyle are not significant factors
The cervix normally stays closed until labour begins. However, if the cervix has become weak, a condition known as cervical incompetence, the weight of the growing fetus and its surrounding amniotic fluid may cause the cervix to open early, resulting in a miscarriage. Cervical incompetence is the cause of about 1 in 4 miscarriages after the 14th week of pregnancy.
The cervix may be weakened by previous surgery, such as a cone biopsy (see Treating cervical intraepithelial neoplasia), or by any procedure that involves artificial opening of the cervix. For example, a woman who has had more than three pregnancy terminations at an early stage is more likely to develop cervical incompetence.
Often there are no symptoms of cervical incompetence before miscarriage occurs. At this stage, the mother may feel pressure in the lower abdomen or a “lump” in the vagina.
What might be done?
If you have had a previous miscarriage after the 14th week of pregnancy, your doctor may arrange for you to have ultrasound scanning to check for cervical incompetence. The scan is performed through the vagina to measure the thickness of the cervix and may be carried out at an early stage in your next pregnancy or when you are planning a pregnancy. If you are at high risk of cervical incompetence, possibly due to previous surgery on the cervix, you may also be investigated for cervical incompetence before or early in pregnancy.
If the cervix is weak, a stitch can be inserted in it to hold it closed. The procedure is carried out under general or epidural anaesthesia between weeks 12 and 16 of pregnancy. The stitch is usually removed at 37 weeks, before the beginning of labour. If labour starts while the stitch is still in place, it will be removed immediately to prevent the cervix from becoming torn. If the stitch fails to prevent a miscarriage, another pregnancy may be successful if a stitch is inserted higher in the cervix, sometimes during an abdominal operation.
Cervical incompetence is likely to recur in subsequent pregnancies, so the cervix may need to be stitched each time to prevent miscarriage.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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