Cervical shortening
The cervix is the lower third of the uterus, the part that opens into the vagina. It has a job to do in pregnancy – it should stay firm and closed during the pregnancy, so that the baby stays put. In late pregnancy, when it’s time for labor to start, the cervix should soften, shorten (efface), and open to allow the baby to be born. Simple, right? Sometimes, though, the cervix begins softening and shortening earlier in pregnancy than it should. Cervical shortening increases the risk of preterm birth. That’s what happened to Pam.
Pam was sent up to my office after a routine ultrasound at 20 weeks showed that her cervix looked short. She felt fine. She was a fifth grade teacher, and this was her first pregnancy. When I looked at her cervix with vaginal ultrasound, her cervix was short, just as her OB had suspected. Normally, your cervix should be more than 3 centimeters long, from the internal opening to the external opening in the vagina. Pam’s cervix measured about 1 cm. I talked to her about the risk of delivering early. We discussed management options, which included daily vaginal progesterone, cervical cerclage, or expectant management. I explained:
• Vaginal progesterone: Progesterone is a hormone that your ovaries normally make. During your menstrual cycle, progesterone helps develop the lining of the uterus in preparation for pregnancy. In pregnancy, progesterone helps keep the cervix firm and reduce contractions. In women with cervical shortening (cervical length less than 2 cm), vaginal progesterone has been shown to reduce the risk of preterm birth by 30-40%. The medication is usually provided in cream or suppository form.
• Cervical cerclage: A cerclage is a suture, or stitch, that is surgically placed to keep the cervix closed. Some women who have had a history of very preterm birth related to cervical shortening (or “incompetence”) have a cerclage procedure at the end of the first trimester. Recent studies have shown that, although a cerclage is not a magic cure for short cervix, it can help to keep the cervix closed in women whose cervix shortens in pregnancy.
• Expectant management: Some women choose to decline both cerclage and vaginal progesterone, and take their chances with cervical shortening. This is not an unreasonable option, since not everyone with a short cervix goes on to deliver prematurely. However, if you decline treatment and your cervix begins to open, in addition to shortening, we have very limited options at that point.
Pam decided to try vaginal progesterone at first. She continued to work every day. It was hard for her to feel very concerned about her cervix, because she felt fine, with no cramping or contractions. She returned to the office a week later, and on that visit, her cervix had shortened even more, and was now slightly open and less than 1 cm long. At that point, we admitted her to the hospital and placed a cerclage. She was now 21-22 weeks. She was able to go home the following day, and she did not return to work. At 23 weeks, her membranes ruptured, and she was admitted to the hospital. At 24 weeks, she went into labor and delivered Justin, a tiny baby boy. Justin lived for three months in the NICU, but finally succumbed to complications of prematurity.
Unfortunately, the way that most women find out that they have a soft or incompetent cervix is to lose a baby. Recently, more OBs have started routinely measuring cervical length at about 20 weeks of pregnancy, so that treatment can be offered if the cervix is shortened. In women with a history of preterm birth, weekly progesterone injections are now offered with subsequent pregnancies, sometimes in addition to cerclage. A “prophylactic” cerclage is one that is placed before the cervix begins to shorten. The decision to place a cerclage is based on whether a previous premature birth was felt to be due to an incompetent cervix rather than preterm contractions. Progesterone is a better option to reduce contractions. Cerclage may help to give the cervix extra support, but will not prevent contractions. It is our job as OB providers to review your history with you and plan together what the best course of treatment is for you.
On a bright note, Pam delivered a healthy baby girl at full term just last week. She received weekly progesterone injections and a prophylactic cerclage with this pregnancy, and had no complications at all. Mom and baby are doing well, and my heart gives thanks for Pam’s resilience and determination to try again.