I found Dr. Norwitz’s “Assessing preterm birth risk: from bulletin to bedside” [March], intriguing. I am a labor and delivery nurse at a teaching facility licensed for 500 beds, and I found most of the risk factors listed in the article to be similar to what I see in our patients. For example, the demographic characteristics, including race, socioeconomic status, low pre-pregnancy weight, maternal age, and absent or inadequate prenatal care are evident in more than half the patients seen in the department.
Many of our high-risk patients successfully receive cervical cerclage. However, I have witnessed several incidents where a patient contracted more with a cerclage than without. When the cerclage was removed, the patient stopped contracting and remained stable. Our residents also perform fetal fibronectin (fFN) testing, and the results often are accurate.
Allison Richardson, RN
Dr. Norwitz responds:
Ms. Richardson’s comments highlight some of the difficulties in managing parturients at risk of preterm birth. Risk-factor screening is neither sufficiently sensitive nor specific to be of much clinical value. Presently, the best screening tests available include fetal fibronectin (fFN) testing and sonographic measurement of cervical length. However, even these tests are recommended only for women with symptoms suggestive of preterm labor.
It is important to note that cervical cerclage is the treatment of choice for women with cervical incompetence. It is not appropriate prophylaxis for women at risk of preterm labor. It certainly should not be used to treat women with symptoms of preterm labor. Indeed, the presence of uterine contractions is an absolute contraindication to cervical cerclage. Uterine contractions may increase transiently around the time of cerclage placement due to prostaglandin release. This is especially true of emergent cerclage, i.e., placement of a cerclage after evidence of cervical effacement and/or dilatation, which is why many practitioners will administer indocin at the time of emergent cerclage placement. However, the presence of a cervical cerclage remote from placement has not been shown to cause uterine contractions.