During pregnancy, as the fetus grows heavier, it presses on the cervix. When the baby comes to term, the cervix is one of the major indicators of impending birth. But in less than two percent of all pregnancies in the U.S., cervical insufficiency upends this process and puts the fetus at risk. Formerly known as incompetent cervix, this condition causes nearly a quarter of the premature births and miscarriages that occur between 14 and 20 weeks.
As early as the 17th century, doctors noted that late-term pregnancy loss was caused by cervical abnormalities. It wasn’t until the mid-1860s that “cervical incompetence” was first used as a medical term. Then, in the mid-20th century, the accepted term became “cervical insufficiency,” and the condition was clinically associated with repeated late-pregnancy losses.
The cervix is a band that protects against fetal loss. Located in the lower uterus, it is thick and fibrous, and along with mucous glands, helps create a protected and sterile environment for fetal development. An insufficient or weakened cervix dilates and thins before term; it is unable to bear the weight of the growing fetus without medical intervention.
Tightness in the belly, along with urinary tract infections and sticky, white vaginal discharge are normal occurrences during the second trimester. However, a backache that wasn’t there before, as well as spotting for numerous days or weeks, are problematic symptoms of which expectant mothers need to be aware. The most worrisome symptom is painless cervical dilation and effacement without the water breaking, occurring before the 24th week. Unfortunately, without a prior history, there is no way to predict cervical insufficiency.
A number of issues can lead to cervical insufficiency or incompetent cervix. Some women have congenital malformations of the cervix. Those who had dilation or curettage (D&C) from termination or miscarriage, could also have a weak cervix. Surgery to treat detected pap smear abnormalities can also contribute to the condition. While rare, women who experienced a cervical tear from a previous difficult delivery may develop a weak cervix that becomes an issue for future pregnancies.
In some cases, prescription drugs can cause an incompetent cervix. Between 1938 and 1971, doctors administered a synthetic nonsteroidal estrogen called diethylstilbestrol, DES, to women to prevent pregnancy complications. It turned out that DES increased the risk of certain vaginal and cervical cancers, as well as breast cancer. The daughters of women who took DES while pregnant face an increased risk of breast cancer, as well as difficulty conceiving, miscarriage, or premature births due to abnormalities in the vagina and cervix.
The only time a doctor can detect an incompetent cervix is during pregnancy. This is even more challenging during a first pregnancy, because the doctor may not know to look for the condition. If a woman experiences symptoms of cervical insufficiency, a pelvic exam can determine if the amniotic sac is protruding through the cervical opening, and transvaginal ultrasound can provide a better picture. In conjunction with the ultrasound and exam, the doctor will order lab tests to check for inflammation and infection of the amniotic sac.
For some cases, doctors may prescribe the hormone progesterone, which helps uterus growth during pregnancy and reduces early contractions that can lead to miscarriage. Vaginal progesterone comes in suppository, capsule, and gel form and is prescribed for daily use between 24 and 37 weeks. This is not the best solution for everyone, especially for women who pregnant with multiples.
Also known as a cervical stitch, cervical cerclage is an outpatient procedure that takes place at a hospital under general anesthesia, with ultrasound for guidance. There are three types. The McDonald operation involves a needle to stitch the outside of the cervix. The Shirodkar procedure uses ring forceps that pull the cervix while pulling back the vaginal walls, to make incisions and stitches at the juncture where the vagina and cervix meet. Transabdominal cervical cerclage is a laparoscopic procedure that involves elevating the uterus and then stitching like Shirodkar.
After the procedure, the woman may experience spotting for a few days and is at risk for inflammation and cervical laceration. Removing the cerclage has its own risks, as well. The McDonald version can be removed, as can the transabdominal, especially in the case of C-section deliveries. With the Shirodkar, the doctor can leave the cerclage in if a C-section is scheduled. However, it should be removed if the woman chooses to become pregnant again, as it can affect future fertility.
A pessary is a round, silicone medical device placed around the cervix to close it. The doctor places it at the opening between the 12 and 14 weeks. It is removed when the risk of preterm delivery has passed. One studies suggests installing a cervical pessary cuts the rate of premature birth by more than half compared to cases where it was not inserted. Scientists are looking at pessaries as a less risky alternative to cerclage.
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