Why is my cervix important in pregnancy?
Imagine your uterus is a balloon (currently filled with baby, placenta and the waters) – then your cervix is the knot in the balloon holding everything in!
More accurately, it’s the tube of muscle at the bottom of your womb. During pregnancy the tube stays long and tightly closed. Normally, the cervix only starts to shorten and open up when you have reached full term and the baby is ready to be born.
In some women, the cervix can’t hold on until the end of the pregnancy. The cervix starts to shorten and dilate prematurely, usually without any pain or contractions. This is sometimes called cervical insufficiency.
What if my cervix starts to open too soon?
Miscarriage and premature birth can both result from the cervix opening too soon.
Premature (or preterm) birth means delivery before 37 weeks gestation. In New South Wales, 5-10% of all babies are born prematurely. Most babies with serious complications of prematurity are born before 34 weeks.
Miscarriages caused by cervical insufficiency occur later than most miscarriages, often around 14-20 weeks.
How can I check my cervix?
All pregnant women should have a fetal anatomy scan at 18-20 weeks. As part of this scan, the sonographer measures the cervical length to identify women who have a short cervix (less than 25 mm). Women who have a short cervix at the 18-20 week scan have a higher than average risk of preterm birth.
My cervix is short on my 19 week scan – what is my chance of delivering prematurely?
Women with a cervical length less than 25mm have a 30% risk of preterm delivery. If the cervix is less than 15mm, the chance of preterm delivery is 50%.
My cervix was short in my last pregnancy – what do I do next time?
Any woman with a history of a short cervix or premature birth is at risk of the same thing happening in the next pregnancy. Ideally, you should have pre-pregnancy counselling to determine any underlying causes and make a plan for when you conceive.
Once you are pregnant, you should have an early visit (around 8 weeks) with a Maternal-Fetal Medicine specialist. You will need extra monitoring and to discuss treatments that reduce your risk.
What treatments are available?
There are essentially 3 options for women with a short cervix. The best option will depend on your individual circumstances and should be discussed with a Maternal-Fetal Medicine specialist. The options are:
- Observe closely – even women with a short cervix are most likely to deliver at term
- Commence vaginal progesterone medication to reduce the risk
- Insert a cervical stitch (cerclage) to reduce the risk