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Anteroposterior Diameter of the Upper Cervix: A Potential Marker for Cervical Insufficiency [A240]

INTRODUCTION: Having observed an apparent smaller cervical diameter on clinical examination in patients presenting for cerclage because of a history of cervical insufficiency in all prior pregnancies (congenital cervical insufficiency [CCI]), an observational study of upper cervical anteroposterior diameter (APD) was undertaken of this measurement in the second trimester of CCI patients (n=86, 28.4%), utilizing APD in a comparison group of patients from a general obstetric practice (normal, n=217, 71.6%) with prior obstetric histories devoid of preterm deliveries. METHODS: APD (expressed in millimeters) was measured in each group on images taken for clinical use in both groups between 14 completed weeks and 23+6 weeks gestation. Patients with cerclage in place, cervical surgical treatment or damage and multifetal pregnancies were excluded. Analysis of central tendency and variation were undertaken in each group. RESULTS: The APD (mean ± standard deviation) was 32.0±4.3 mm in the CCI group and 40.6±5.2 mm in the normal group. The gestational age of the measurement taken at the ultrasound was included as a covariate in a generalized linear model. There was a statistically significant difference in the size of the APD between the normal group and the CCI group (t=7.08, P<.001). CONCLUSION: This preliminary, exploratory study suggests that upper cervical diameter may be a marker to distinguish patients seen in their first pregnancy who are at risk for clinical manifestation of cervical insufficiency. A much larger prospective study of primigravid patients will be necessary to verify this relationship.