short cervix

ervical insufficiency (short cervix)
HS GS: Pregnant woman sitting and reading

Dear Doctors Column, April 28, 2008


My sister is 24 weeks pregnant and her doctor says she has a short cervix, which he plans to monitor with weekly ultrasounds. What can you tell me about this condition?


The cervix is the narrow, cylinder-shaped base of the uterus that extends into vagina. A short cervix is just that – a cervix that is shorter than normal. Cervical length is typically about 2.5 cm. Having a cervix that is shorter than normal may increase the risks of miscarriage and preterm birth. Women with a short cervix also can have a cervix that is softer or weaker than normal, a condition called cervical insufficiency or incompetence.

During normal pregnancies the cervix stays firm and closed until late in the third trimester. When the cervix is shorter or softer and weaker than normal, the growing weight of the baby can cause the cervix to start opening (dilating) before labor begins. This can cause second trimester miscarriage, preterm delivery (before 37 weeks), or early preterm delivery, which is giving birth before 32 weeks.

Until recently women rarely knew they had a short or weakened cervix until they experienced a miscarriage or preterm delivery late in pregnancy. A technology called transvaginal ultrasound now makes it possible for doctors to evaluate cervical length and other characteristics. Although this kind of examination is not usually part of routine care, a doctor may perform the test if he feels a patient is at risk for preterm delivery.

Once a short or weakened cervix has been diagnosed, as with your sister, it’s common for obstetricians to use weekly ultrasounds to monitor the cervix for changes – sudden shortening or dilation – that might signal a miscarriage or early birth. Advance knowledge of a preterm birth can give your doctor time to administer corticosteroid shots, which can help the fetus’s lungs develop and limit future health problems in premature babies.

Although there is much research underway in this area, physicians still don’t have a treatment that’s proven totally effective for preventing miscarriage or preterm birth caused by a short or weakened cervix. Doctors sometimes recommend bed rest and pelvic rest (no sex, douching, or tampons). There’s no solid evidence these precautions work, but the theory is that limiting stimulation and weight on the weakened cervix might prevent early delivery.

Doctors also may suggest a cerclage, stitch in the cervix that’s intended to keep it from opening too early. The stitch is usually removed around the 37th week of pregnancy. Use of the cerclage is controversial, as some clinical studies have shown a benefit from the stitch while others found the procedure was ineffective at delaying birth.

Researchers are studying other methods, such as progesterone injections, to prevent miscarriage and preterm delivery caused by a short or weak cervix. Once you’re diagnosed with a short or insufficient cervix, you’ll have an increased risk of miscarriage and preterm delivery during future pregnancies. That’s why it’s crucial to tell your doctor about any previous problems found with your cervix and any prior miscarriages or early deliveries.

Always call your health care provider right away if you have painful contractions, fluid leaking from the vagina, menstrual cramping, or pelvic pressure or heaviness

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