Relationship between endocervical canal length between 15-24 weeks gestation and obstetric history

The object was to determine whether there is a correlation between the obstetric history and the ultrasonographically determined endocervical canal length between 15 and 24 weeks gestation. A retrospective cohort study was performed in singleton pregnancies of multigravidas with normal and abnormal obstetric histories. They underwent sonographic evaluation for the determination of the endocervical canal length between 15 and 24 weeks gestation. The shortest endocervical canal length measurements between 15 and 20 weeks and also between 21 and 24 weeks of gestation were recorded. An ultrasound diagnosis of cervical incompetence was defined as progressive shortening of the endocervical canal length to <2 cm or a single endocervical canal length measurement <2 cm. A multivariable general linear regression model was used to correlate the relationship between endocervical canal lengths at 15-20 weeks and 21-24 weeks gestation in the current pregnancy with the earliest gestational age at delivery of prior pregnancies. Chi-square test was used to determine the relationship between the development of an ultrasound diagnosis of cervical incompetence and the earliest gestational age at delivery of prior pregnancies. A total of 155 pregnancies were studied. The number of women according to the obstetric history categories were: 57 had delivered <24 weeks, 12 between 24 and 26 weeks, 16 between 27 and 32 weeks, 16 between 33 and 36 weeks, and 54 delivered > or =37 weeks. There was a significant correlation between the endocervical canal length measurements between 15-20 (P < 0.0001) weeks and 21-24 weeks (P < 0.0001) in the studied pregnancy and the earliest gestational age at delivery of prior pregnancies. A significant relationship between the ultrasound diagnosis of cervical incompetence and the obstetric history category (P = 0.0026) was observed. There were 36 cases of ultrasound diagnosed cervical incompetence with 91.7% (33/36) occurring in women who had a prior <27 weeks' gestation delivery. These data provide further evidence that cervical incompetence is a relative condition and not an "all or none" phenomenon. In addition, women with a prior delivery <30 weeks gestation should be followed with second trimester serial cervical sonography to rule out cervical incompetence.