Cervical competence as a continuum: A study of ultrasonographic cervical length and obstetric performance

OBJECTIVE: Our purpose was to investigate the hypothesis that cervical competence is a continuum that is related to cervical length and is reflected by pregnancy history. STUDY DESIGN: A cross-sectional study was performed of cervical length measured by transvaginal ultrasonography in women with prior preterm delivery at ≤ 26 weeks, 27 to 32 weeks, and 33 to 35 weeks compared with women with cervical incompetence and normal controls delivered at term. RESULTS: Transvaginal cervical length was measured during pregnancy in 32 subjects with cervical incompetence, 98 with previous preterm birth ≤ 26 weeks, 98 with previous preterm birth at 27 to 32 weeks, 127 with previous preterm birth at 33 to 35 weeks, and 106 normal controls. The relationship between obstetric history and cervical length was evaluated by analysis of variance. The gestational age at the first preterm delivery was significantly correlated with cervical length in the current pregnancy at each gestational interval between 20 and 30 weeks in a continuous manner. CONCLUSION: Cervical competence is a continuous rather than categoric variable and is indicated indirectly by measurement of the length of the cervix.