In pregnancy, if your cervix begins to dilate in your second trimester of pregnancy (14 through 27 or 28 weeks), your obstetrician is faced with some tough decisions. Are you actually in preterm labor, headed for a miscarriage, or is your cervix dilating and endangering your baby for some other reason?
It’s possible if you are in actual labor, your baby simply can no longer survive in your uterus. But it’s also possible that your cervix for some reason isn’t staying closed enough to support your baby as long as needed to go full term, and you are not really in true labor.
If you are not genuinely in labor and your cervix is thinning, obstetricians will possibly use the term incompetent cervix to describe your condition. This label has been in use for a long time by health care practitioners but gives the unfortunate connotation that the woman is somehow responsible for having a cervix that doesn’t do its job.
If your cervix begins to thin in your second trimester but the baby’s amniotic sac has not broken, and at the same time your obstetrician believes no true labor is occurring, he or she may suggest surgically sewing your cervix shut in a procedure called cerclage. The stitches are then removed in the 37 th week of pregnancy or before true labor begins.
Until relatively recently, subclinical (undetected) infections have been widely overlooked as a cause of midterm cervical dilation. If you are faced with the problem of cervical dilation in your second trimester, ask your doctor about infection of the amniotic sac and membranes (chorioamnionitis).
If you have miscarried or delivered preterm in a previous pregnancy, the greatest risk factor for another preterm delivery is your first preterm delivery or a previous preterm loss. In my practice, I always considered incompetent cervix a sign of infection until I could prove otherwise because infection is a contraindication for cerclage. I would check for gonorrhea, chlamydia, ureaplasma, microplasma, group B strep, bacterial vaginosis, and trichomonas.
Once you have a diagnosis of incompetent cervix, your obstetrician knows the risk of a repeat preterm delivery is significant and may even suggest cerclage as a preventative measure. Even in this situation, I did my best to first rule out infection.
We now know that undetected infections are a major cause of midterm and preterm labor. Once infection has been ruled out and you are known to not be in labor, and your cervix is thinning, you may be a candidate for cerclage.